Calculator
Enter your sex, age, height, weight and how active you are, and this calculator estimates your resting energy, or basal metabolic rate (BMR), with the Mifflin-St Jeor equation, and your daily calories, or total daily energy expenditure (TDEE), using physical activity levels (PALs) measured in real people rather than guessed multipliers. It shows the other main equations alongside, the NHS advice on cutting calories, and how far out an estimate can be. Use the result as a starting point: your weight over the next few weeks is the real test.
Enter your sex, age, height and weight, in centimetres and kilograms, feet and stones, or feet and pounds, and choose how active you are. You can also add a body fat percentage, pick another equation, give your family background and choose a goal, and tick a box if you're pregnant, breastfeeding, or take insulin, a diabetes tablet or a weight-loss medicine.
2,750kcal
Many people's true figure is within about 10% of this (2,450 to 3,000 kcal), but the wrong activity level can put you outside it. Resting energy (BMR): 1,720 kcal (7,190 kJ).
| Equation | BMR | × 1.6 |
|---|---|---|
| Mifflin-St Jeor (1990)Within 10% for the most people in independent tests. | 1,720 | 2,750 |
| Henry (Oxford, 2005)The UK reference, used by SACN. | 1,730 | 2,780 |
| Harris-Benedict (1919)The original; it ran about 5% high in Mifflin's study. | 1,790 | 2,860 |
| Roza-Shizgal (1984)The 1984 refit of Harris-Benedict. | 1,790 | 2,860 |
| Schofield (WHO/FAO)Tends to run high in many populations. | 1,790 | 2,870 |
The US 2023 reference equations, fitted to measured daily energy use, give 2,600 kcal (inactive), 2,820 kcal (low active), 3,000 kcal (active), 3,360 kcal (very active). They're typically 250 to 340 kcal a day out for one person.
This is an estimate. Weigh yourself once a week for 2 to 4 weeks: if your weight is steady, you've found your figure; if not, adjust by about 100 to 200 kcal. The NHS average is 2,000 kcal for women and 2,500 for men.
The calculator starts with Mifflin-St Jeor: for women, 10 × weight in kg + 6.25 × height in cm - 5 × age - 161; for men, the same + 5. It was built from 498 healthy adults aged 19 to 78, nearly half of them with obesity, and independent reviews find it within 10% of measured resting energy for more people than the other common equations.
In 337 adults, Mifflin-St Jeor was within 10% for 82%: 87% of those without obesity and 75% of those with it. In healthy older adults, no equation was both accurate and precise. So the result comes with a range, and your weight over a few weeks is the real check.
Studies that measured daily energy use put the typical UK adult at 1.63 times their BMR, with a quarter below 1.49 and a quarter above 1.78. The common 1.2 multiplier is the level of someone confined to a bed or chair, so the calculator uses four levels from 1.4 to 2.0, based on those measurements, instead.
The NHS says an average woman needs about 2,000 kilocalories (kcal) a day and an average man about 2,500. The Scientific Advisory Committee on Nutrition's (SACN's) reference values vary by age: 2,175 kcal for women aged 19 to 34 and 2,629 for men aged 35 to 44, for example.
The NHS suggests eating about 600 kcal a day less and aiming to lose 0.5 to 1 kg a week. The National Institute for Health and Care Excellence (NICE) sets no fixed deficit, and keeps diets of 800 to 1,200 kcal a day for specialist services with support, so the calculator never shows a target below 1,200.
In a validated model, a cut of 480 kcal a day takes a 100 kg man to a plateau about 25 kg lighter over several years, half of it in the first year; the 3,500-calories-per-pound rule predicts about twice as much in year one. The body's own slowing is usually small. So the calculator gives calories, not a date or a weight.
Your basal metabolic rate (BMR) is the energy your body uses at rest. It's usually 45 to 70% of the energy adults use in a day. The calculator works it out from your sex, age, height and weight with the equation you choose, and shows it to the nearest 10 kcal, with kilojoules (kJ; 1 kcal is 4.184 kJ).
The equations were built with sex as recorded in the studies. If you're not sure which fits your body, try both (our suggestion).
Written as the authors simplified it, with weight in kg, height in cm and age in years. Their full version is "REE = 9.99 x weight + 6.25 x height - 4.92 x age + 166 x sex (males, 1; females, 0) - 161", where REE is resting energy expenditure, and they say simplifying it "did not affect its predictive value"; the two differ by 1 to 4 kcal a day in our examples (our arithmetic). It was built from resting energy measured in 498 healthy adults (247 women and 251 men) aged 19 to 78, 264 of them in the normal weight range and 234 with obesity.
Source 1
You can pick any of these instead, and "See every formula" under the result shows them all. Weight in kg, height in cm, age in years, results in kcal a day:
As SACN prints them (Table 18), in megajoules (MJ) a day, with weight in kg and height in metres. The calculator converts to kcal at 4.184 kJ per kcal.
As FAO/WHO/UNU print them (Table 5.2) and SACN repeats them for adults, in kcal a day from weight in kg, with each equation's standard error in brackets:
Some copies of these equations differ, so this is what we used:
Daily calories = BMR × your physical activity level (PAL): your total daily energy use divided by your BMR, as measured with doubly labelled water. Your usual exercise is part of your level, so don't add exercise calories on top.
The four levels use the European Food Safety Authority's (EFSA's) values, with examples from the US 2023 reference report to describe them (the descriptions are ours):
Many calculators multiply BMR by 1.2, 1.375, 1.55, 1.725 or 1.9. We couldn't trace that ladder to a study: a 2022 paper cites Mifflin's 1990 paper for it, but that paper's abstract has no activity factors, and a 2026 study that uses two of the steps cites a review that doesn't give them. The steps are evenly spaced, with 1.375 halfway between 1.2 and 1.55 and 1.725 halfway between 1.55 and 1.9 (our arithmetic), so it looks like a convention.
It also sits low against the measurements. About 1.2 is the level of people confined to a bed or chair, SACN says 1.38 "seems the likely lower limit for free-living individuals", and FAO/WHO/UNU's own example treats 1.55 as sedentary, where the ladder calls it moderate. For someone at the UK's 25th centile, 1.49, using 1.2 gives an answer about a fifth too low (1.2 ÷ 1.49 = 0.81; our arithmetic).
Your BMR to the nearest 10 kcal, with kJ, and your daily calories to keep your weight steady, also to the nearest 10 kcal, with a range rounded to the nearest 50 kcal: many people's true figure is within about 10% of it. The range reflects validation studies, where about 8 in 10 people were within 10% of their measured resting energy, and the US equations' average error of about 9%. It's a typical range, not a guarantee, and the wrong activity level can put you outside it (our choice). The NHS averages, 2,000 kcal for women and 2,500 for men, sit underneath.
Every result says it's an estimate: weigh yourself once a week for 2 to 4 weeks, and if your weight is steady you've found your figure; if not, adjust by about 100 to 200 kcal. That's the US report's approach of checking your weight and adjusting; the step size is our choice.
Lose weight: your daily figure minus 600 kcal, never below 1,200, with the NHS aim of 0.5 to 1 kg a week and a reminder that loss slows. It's offered only if your body mass index (BMI) is 25 or more, or 23 or more if you choose one of the backgrounds NICE lists (South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean), because that's where NICE's overweight range starts; otherwise the page says why. Gain weight: plus 300 to 500 kcal, offered at a BMI under 18.5.
Pregnant: guidance instead of numbers. Breastfeeding a baby under 6 months who has only breast milk: your figure plus 330 kcal, with no weight-loss line. Insulin or a diabetes tablet such as gliclazide: a warning about low blood sugar. A weight-loss medicine: a note to keep up strength training and enough protein. Choose to lose or gain weight and you'll also see where to get help with eating disorders.
Under 18 the calculator stops, because the equations are for adults. From 80 it notes that fewer people that age were in the studies: Mifflin's oldest was 78.
"See every formula" also gives the US National Academies' 2023 equations, which predict daily energy use directly from age (years), height (cm), weight (kg) and an activity category: inactive (a PAL under 1.53), low active (1.53 to 1.68), active (1.68 to 1.85) or very active (1.85 to 2.50). They were fitted to doubly labelled water measurements in about 5,600 adults, and for one person they were out by 9.4% (men) and 8.7% (women) on average, with typical errors of 339 and 246 kcal a day.
The report's own example, a woman of 22, 165 cm and 63 kg who is low active, comes to "2,275 kcal/day"; the calculator gets 2,275.37 before rounding, shown as 2,280 (our arithmetic).
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Rounded as the calculator rounds them. In these examples and the floor example under "Cutting calories safely", Mifflin-St Jeor gave the lowest or second-lowest BMR of the five equations that don't need body fat, and those five spread by 4 to 14%.
A systematic review for the American Dietetic Association found "the Mifflin-St Jeor equation was the most reliable, predicting RMR within 10% of measured in more nonobese and obese individuals than any other equation, and it also had the narrowest error range" (RMR is resting metabolic rate), though older adults and US ethnic minorities were underrepresented. In 130 adults with BMIs from 18.8 to 96.8, it was more than 10% out for 22%, against 33% for Harris-Benedict and 35% for the Owen equation. In 337 adults it was unbiased on average (95% confidence interval -26 to +8 kcal a day), and in 338 US adults with BMIs of 25 to 40 it was within 10% for 79%.
In 337 community-living adults, Mifflin-St Jeor was within 10% of measured resting energy for 82%: "87 vs. 75%" in people without and with obesity. A review of adults with a BMI of 25 or more found about 75% of its predictions within 10% and errors above 10% in 25%, and concluded that "No single prediction equation provides accurate and precise REE estimates in all obese adults". In Dutch adults with overweight or obesity, "there appears to be no accurate equation".
A 2022 meta-analysis of 61 studies in adults with overweight and obesity found Harris-Benedict the most precise, with 60.65% and 62.54% of predictions within 10%, and Schofield the least biased with overweight; "Equations with body composition data showed the highest biases". During weight loss, Harris-Benedict showed the smallest differences at 3, 6 and 12 months, with wide prediction intervals. An earlier review found Mifflin-St Jeor the most precise at BMIs of 30 and above, and Henry the most accurate at 40 and above.
In healthy older adults, no equation was both accurate and precise. Mifflin-St Jeor had the least bias (-0.3%) and Harris-Benedict +2.6%, but only about 70% (Harris-Benedict), 65% (Henry) and 61% (Mifflin-St Jeor) of predictions were within 10%. In athletes (29 studies, 1,430 people), Mifflin-St Jeor misestimated resting energy on average, while the lean-mass and Harris-Benedict equations didn't, though results varied widely between studies.
Henry's Oxford equations came from 10,552 measurements. They left out the Italian data that made up 47% of Schofield's, added 4,018 people from the tropics, and predict a lower BMR than Schofield's for men aged 18 to 60 and for all women; Henry writes that the FAO/WHO/UNU equations "overestimate BMR in many communities". SACN uses Henry's for UK energy values, though "there does not appear to have been any recent validation within the current UK population". In 767 US adults with measured BMR, Henry was within 10% for 73% and Schofield for 69%. EFSA considers Harris-Benedict, Schofield, Mifflin-St Jeor, Müller and Henry equally valid for healthy European adults.
Doubly labelled water studies measure total energy use in daily life; divided by BMR, that gives the physical activity level. SACN's UK reference is a median of 1.63, with 1.49 and 1.78 at the 25th and 75th centiles. FAO/WHO/UNU class 1.40 to 1.69 as sedentary or light, 1.70 to 1.99 as active and 2.00 to 2.40 as vigorous, and say values above 2.40 "are difficult to maintain over a long period of time". EFSA uses 1.4, 1.6, 1.8 and 2.0, and notes that sustainable lifestyles range "between 1.35 and 2.5". In 574 measurements, the limits of daily energy use were about 1.2 and 4.5 times BMR.
The US 2023 report says "a valid, reliable tool does not exist to enable accurate classification of an individual's PAL category", and that the categories "do not correspond to the physical activity guidelines". SACN found that "predictions of PAL values are unlikely to be accurate": in studies classed as light activity, average PALs ranged from 1.23 to 1.98. So if your weight changes at your chosen level, adjust (our suggestion).
We looked for the origin of 1.2, 1.375, 1.55, 1.725 and 1.9. A 2022 paper gives all five and cites Mifflin 1990, whose abstract has no activity factors; a 2026 study uses 1.375 and 1.725 and cites a 2023 review of athletes that doesn't give them. Not finding a source doesn't prove there isn't one, so we grade this mixed, but the measured values the calculator uses are far better documented (our reading).
FAO/WHO/UNU say their energy requirements "are to be applied to population groups and not to individuals". The US 2023 report calls choosing an activity level "the most challenging aspect" of estimating someone's needs, and advises people to "monitor body weight over time" and adjust. Even its own equations, fitted to measured daily energy use, are typically 250 to 340 kcal a day out for one person.
NHS Better Health: "To lose weight, you need to eat and drink fewer calories than you do now. Aim to reduce your intake by around 600 calories a day. This is a safe and sustainable way to lose weight." The NHS also advises losing weight steadily, aiming for 0.5 to 1 kg (1 to 2 lb) a week, and says "Just losing a small amount of weight (5 to 10% of your body weight) can improve your health".
NICE's 2025 guideline asks for dietary approaches that "keep the person's total energy intake below their energy expenditure (also called an energy deficit or calorie deficit)", offered with support and follow-up. On the size of the cut, its committee found that studies varied: "Many used a 500 to 800 kilocalories a day deficit but it was also common to use an individual deficit for each participant, so they agreed not to specify a particular deficit."
NICE says to consider diets of 800 to 1,200 kcal a day "only as part of a multicomponent overweight and obesity management strategy with long-term support within a specialist overweight and obesity management service", and under 800 kcal only for people with a clinically assessed need to lose weight quickly, such as to make surgery safer. These diets should be nutritionally complete, last no more than 12 weeks and come with ongoing clinical support, and before starting, clinicians should check for eating disorders and review any medicines. The NHS: "Very low calorie diets are not suitable or safe for everyone."
The 2013 US obesity guideline says to "Prescribe 1200-1500 kcal/d for women and 1500-1800 kcal/d for men (kilocalorie levels are usually adjusted for the individual's body weight)", or "an energy deficit of 500 kcal/d or 750 kcal/d or 30% energy deficit", and keeps diets under 800 kcal for limited circumstances, run by trained practitioners in a medical care setting. The US National Institutes of Health's (NIH's) Body Weight Planner won't set a target below 1,000 kcal a day, because "Food group targets and nutrient recommendations will not be met below 1000 calories/day".
Because NICE keeps 800 to 1,200 kcal diets for specialist services, the calculator never shows a weight-loss figure below 1,200 kcal a day (our choice). If 600 kcal less would take you below that, it shows 1,200 and says the cut is smaller, with a pointer to your GP, who can advise on losing weight safely and refer you to weight management programmes. If your daily figure is already 1,200 or less, it shows no weight-loss figure at all, only the pointer to your GP.
An example (our arithmetic): a woman of 60, 150 cm and 60 kg (BMI 26.7) who is mostly sitting has a BMR of 1,080 kcal and a daily figure of about 1,510. Taking off 600 would leave about 910, so the calculator shows 1,200, a cut of about 310 kcal.
For adults who need to gain weight, the NHS says they "could try adding around 300 to 500 extra calories a day". See a GP if you've lost weight suddenly or without changing your diet or exercise routine, or if you "use the control of food to cope with feelings". The calculator offers this line at a BMI under 18.5.
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For an average adult with overweight, Hall's validated model found that "every change of energy intake of 100 kJ per day will lead to an eventual bodyweight change of about 1 kg (equivalently, 10 kcal per day per pound of weight change) with half of the weight change being achieved in about 1 year and 95% of the weight change in about 3 years". As you lose weight you need less energy, so the same intake brings slower and slower loss until your weight settles.
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A 100 kg sedentary man who eats 2 MJ (about 480 kcal) a day less settles "at about 75 kg", "taking roughly 1 year to reach half of the maximum weight loss and reaching 95% of this value after about 3 years". The static rule predicted "22 kg lost in the first year", which Hall calls "about 100% greater weight loss than our model prediction".
The paper named the NHS among sources that wrongly said a cut of about 2 MJ a day would bring slow and steady loss of about 0.5 kg a week. So read today's NHS aim of 0.5 to 1 kg a week as an aim, not a forecast (our reading).
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The rule that a pound of fat is 3,500 kcal, so a 500 kcal daily cut loses a pound a week, "grossly overestimates actual weight loss" in seven tightly controlled studies. It roughly matches the energy in weight lost by people starting with more than 30 kg of body fat, but overestimates the deficit needed for each kilo lost by people with less.
In 71 people with obesity eating 1,000 kcal a day for 8 weeks, resting energy was 92 kcal a day below prediction, fell to 38 after 4 weeks at a stable weight, and "metabolic adaptation does not predict weight regain". After extreme weight loss on a television competition, 14 people had regained 41 of their 58 kg six years later, yet their resting energy was still 499 kcal a day below prediction.
NHS Better Health: "Changing what you eat can help you lose weight, but moving more can help you keep the weight off." Our exercise for weight loss guide explains what exercise does well.
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This calculator doesn't turn calories into a date or a weight (our choice). The NIH Body Weight Planner runs a dynamic model of weight change, with activity levels from 1.4 to 2.5, and isn't for under-18s or for use in pregnancy or breastfeeding.
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The NHS: "an average man needs 2,500kcal a day; an average woman needs 2,000kcal a day", and this "could be different based on your: age, weight, height, how much exercise you do". Food labels use a reference intake of 8,400 kJ (2,000 kcal) for an average adult.
SACN's reference values for UK adults at a BMI of 22.5, average heights and a PAL of 1.63, in kcal a day (Table 16):
Source 7
The government's dietary recommendations take SACN's values but cap them "at 10.5 MJ (2500kcal)/day for males and 8.4MJ (2000kcal)/day for females to help address issues of overweight and obesity": 2,500 and 2,000 kcal at 19 to 64, 2,342 and 1,912 at 65 to 74, and 2,294 and 1,840 from 75.
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They're averages for groups. Your own figure depends on your size, age and activity, and can sit well above or below them: the calculator's starting example, a lightly active man of 40 who weighs 80 kg, comes out at 2,750 kcal (our arithmetic).
The NHS says you don't need extra calories for most of pregnancy: "In the final 3 months of your pregnancy, you'll need an extra 200 calories a day", and "even if you are expecting twins or more, you don't need to eat extra portions". Pregnancy "isn't the time to go on a diet", and with obesity, "do not try to lose weight during your pregnancy". SACN adds 191 kcal a day in the last trimester, noting that women who are overweight at the start "may not require this increment", and NICE asks professionals to reassure people "that they do not need to 'eat for two'". So with "I'm pregnant" ticked, the calculator shows this guidance and no figure.
SACN adds 330 kcal a day for the first 6 months of exclusive breastfeeding. Other bodies allow more: the US 2023 report counts about 540 kcal for the milk, less 140 from body stores, and EFSA and FAO/WHO/UNU about 500. The NHS: "You do not need to follow a special diet while you're breastfeeding." With the breastfeeding box ticked, the calculator adds 330 kcal to your daily figure and shows no weight-loss line.
The National Breastfeeding Helpline is on 0300 100 0212. Our guides to exercise in pregnancy and after giving birth cover moving safely.
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The equations are for adults, so the calculator stops. NICE says children's diets should keep intake "at or below the recommended daily calorie intake for their age and sex", and to "Focus on healthy eating rather than on overly restrictive diets". For children and teenagers, the NHS uses a BMI calculator that compares them with others of the same age and sex.
No figure is shown, only the guidance above: don't diet, and expect to need about 200 extra kcal a day only in the last 3 months. Ask your midwife if you're worried about your weight.
The calculator adds 330 kcal for the first 6 months of exclusive breastfeeding, and shows no weight-loss figure.
These numbers aren't the right tool. The calculator shows where to get help whenever you choose to lose or gain weight, and never shows a weight-loss figure below a BMI of 25 (23 for NICE's listed backgrounds). In 493 students, using calorie-counting and fitness-tracking apps went with more eating concern and dietary restraint, and NICE asks clinicians to offer assessment and counselling for possible eating disorders before low-calorie diets. The support section below has the numbers.
The NHS says low blood sugar "is common if you take insulin. It can also happen with some other diabetes medicines, such as gliclazide and glimepiride", for example if you miss or delay meals or don't eat enough carbohydrate. Know Diabetes warns that very low-calorie plans "could significantly increase the risk of hypos" with insulin or sulphonylureas such as gliclazide, and NICE asks clinicians to review medicines before low-calorie diets. Talk to your diabetes team before cutting calories.
The NHS: "You'll need to eat a balanced diet with fewer calories and do regular physical activity while taking them." A 2025 advisory from four US obesity and nutrition societies puts protein and strength training first, because "increased protein intake alone is likely inadequate to support the preservation of muscle mass in the absence of structured resistance/strength training". The protein calculator covers how much.
NHS Better Health advises talking to a GP or another healthcare professional first.
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See a GP if you've lost weight suddenly or without trying. The calculator offers a gain line at a BMI under 18.5.
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Daily energy use can fall to about 1.2 times BMR, below the calculator's lowest level, and Roza and Shizgal found Harris-Benedict "unreliable in the malnourished patient". Ask your care team or a dietitian.
The studies behind the equations included few people this age (Mifflin's oldest was 78), and in older adults fewer predictions fell within 10%, so the calculator adds a note and the estimate is less certain.
1.2 is the floor, seen in people confined to a bed or chair. Free-living adults rarely fall below about 1.38, and the UK median is 1.63.
The rule "grossly overestimates actual weight loss", because weight loss slows as your body gets lighter and settles towards a plateau.
Even the best equation is more than 10% out for about 1 in 5 people, and for more with obesity or in older age. FAO/WHO/UNU say their requirements "are to be applied to population groups and not to individuals".
The body's own slowing averaged under 100 kcal a day during dieting and halved once weight was stable, though it was larger after extreme weight loss. Weight loss slows mainly because a smaller body uses less energy.
In 6,421 people, energy use adjusted for body size was stable from 20 to 60 and fell about 0.7% a year after 60.
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The US guideline's 1,200 to 1,500 kcal for women is a weight-loss prescription "usually adjusted for the individual's body weight". NICE keeps 800 to 1,200 kcal diets for specialist services, and the NHS bases the cut on what you eat now.
A kilo of muscle uses about 13 kcal a day at rest and a kilo of fat about 4.5, so 2 kg more muscle adds about 26 kcal a day (our arithmetic).
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If you have, or think you might have, an eating disorder, these numbers aren't the right tool. See a GP as soon as you can, or talk in confidence to the eating disorder charity Beat: 0808 801 0677 (England), 0808 801 0432 (Scotland), 0808 801 0433 (Wales) or 0808 801 0434 (Northern Ireland). Beat's helplines are open 3pm to 8pm, Monday to Friday, and it also offers web chat and email. If you or someone else is in immediate danger, call 999 or Samaritans on 116 123; for medical advice, contact your GP or call 111.
If you take insulin, or a tablet such as gliclazide or glimepiride, eating less can cause low blood sugar (a hypo). Talk to your diabetes care team before cutting calories, and don't skip or delay meals.
A GP can give you advice about losing weight safely and refer you for treatment, including weight management programmes, medicines and surgery. You may be able to refer yourself to local NHS weight management services without seeing a GP: check your GP surgery's website or ask reception, or search online for NHS weight management services near you.
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If calorie numbers make you anxious, set goals for health and strength instead, such as walking further or lifting a little more (our suggestion, as in our exercise for weight loss guide).
Moving more helps you keep weight off, whatever your goal. A walk after meals and steady cardio are easy places to start; the strength and home workouts add the muscle work.
A 10-minute routine for straight after a meal: an easy walk, a few simple standing moves from blood sugar trials, then a short walk to finish.
10 minBeginner6 movesCardio machine, A bench or boxA steady 30 to 45 minute cardio session at talk-but-not-sing pace: walk, cycle, row or cross-train, counting toward weekly activity guidelines.
40 minBeginner3 movesCardio machine, A wallA 25-minute standing cardio circuit with no jumping: marching, step jacks, sit-to-stands, punches, step-ups and wall push-ups, with a seated option for most moves.
25 minBeginner9 movesA bench or box, A stepA 20-minute full-body dumbbell workout: two supersets of squats, rows, Romanian deadlifts and push-ups. Twice a week covers the minimum dose.
20 minBeginner8 movesA dumbbell, A bench or boxA gentle 20-minute beginner home workout with a chair, a wall and a band: sit-to-stands, wall push-ups, band rows, step-ups and dead bugs.
20 minBeginner11 movesA bench or box, A wallThe NHS says an average woman needs about 2,000 kcal a day and an average man about 2,500, but your figure depends on your size, age and activity. A 35-year-old woman who is 168 cm, weighs 70 kg and walks about an hour a day comes out at about 2,260 kcal on this calculator. Weigh yourself for a few weeks to check it.
BMR (basal metabolic rate) is the energy you use at rest; TDEE (total daily energy expenditure) adds everything else you do, from walking to digesting food. BMR is usually 45 to 70% of the total. The calculator works out TDEE as BMR × your physical activity level, which is about 1.6 for a typical UK adult.
Mifflin-St Jeor has the best record across people with and without obesity: in one study of 337 adults it was within 10% for about 8 in 10. No formula is right for everyone, and in older adults and people with obesity more people fall outside 10%. The UK's nutrition committee uses the Henry equations, and the "Katch-McArdle" formula on many sites is Cunningham's 1991 lean-mass equation, which you can use here by adding your body fat percentage.
The NHS suggests about 600 kcal a day less than you need to keep your weight steady, aiming to lose 0.5 to 1 kg a week. NICE keeps diets of 800 to 1,200 kcal a day for specialist services with support, so this calculator never goes below 1,200, and it shows a weight-loss figure only if your BMI is 25 or more (23 for some backgrounds). If you have a medical condition or an eating disorder, talk to your GP first.
Not in practice. Your body uses less energy as you get lighter, so weight loss slows: in one validated model, a 480 kcal daily cut takes a 100 kg man about 25 kg lighter over several years, roughly half of it in the first year, where the 3,500-calorie rule predicts 22 kg in year one. That's why this calculator doesn't turn calories into kilos or dates.
Mostly because a lighter body burns less. In a study of people on 1,000 kcal a day, resting energy ran about 90 kcal a day below prediction while they were losing weight, and less once their weight was steady. Keep the habits going: eating less does most of the weight loss, and moving more helps keep it off.
Mostly sitting with short walks is 1.4; an hour of walking a day, or a job partly on your feet, is about 1.6, close to the UK average. Choose 1.8 if you're on your feet most of the day or exercise most days, and 2.0 for hard physical work or long daily training. If you're between two, pick one and check your weight over a few weeks.
Not on top of this figure: your activity level already includes your usual exercise, so adding it again counts it twice. If you take up a new activity, our calories burned calculator estimates its cost, and its page explains why watch figures are often well out.
Less than people think. In 6,421 people, energy use adjusted for body size was stable from 20 to 60 and fell about 0.7% a year after 60. So before 60, changes in your needs come mainly from changes in your size, muscle and activity, and strength training helps you keep muscle.
None in the first 6 months of pregnancy, then about 200 a day in the last 3 months (NHS), and you shouldn't try to lose weight while pregnant, so the calculator shows guidance rather than a number. When breastfeeding there's no special diet; UK reference values add about 330 kcal a day for the first 6 months of exclusive breastfeeding, which the calculator adds when you tick the box.
Estimates for healthy adults, not a personal prescription or a diagnosis, and clinical review of these pages is pending. Check with a GP before hard training or testing a maximum if you have a heart condition, high blood pressure, chest pain, dizziness or breathlessness when active, and stop for sharp or increasing pain. Health disclaimer.
