Calculator
Body fat percentage is the share of your weight that's fat. This calculator estimates it from a tape measure with two published formulas: relative fat mass (RFM), which needs your height and your waist at the top of your hip bone, and the US Navy method, which adds your neck (and hips for women). Treat the result as a rough guide: for most people it's within about 5 percentage points of a dual-energy X-ray absorptiometry (DXA) scan, but it can be 10 or more out. No guideline from the National Institute for Health and Care Excellence (NICE), the NHS or the World Health Organization (WHO) sets a healthy body fat range; for health risk, NICE uses your waist-to-height ratio.
Choose your sex and a formula, then enter your height and the measurements it asks for, in cm or in inches with your height in feet and inches.
24%
For most people, within about 5 points either way: roughly 19% to 29%. For some it can be 10 or more out.
Tape formulas tend to read high in lean people, and the Navy method low in people with more body fat. There's no agreed healthy body fat range: no NICE, NHS or WHO guideline sets one. For health risk, NICE uses your waist-to-height ratio, measured midway between your lowest rib and the top of your hip bone: waist-to-height ratio calculator.
If you check your body often in a way that upsets you, a GP can help, and you can refer yourself to NHS talking therapies.
If you have, or think you might have, an eating disorder, these numbers aren't the right tool. See a GP, or talk in confidence to Beat on 0808 801 0677 (England); Beat's helplines lists the numbers for Scotland, Wales and Northern Ireland.
Relative fat mass is 64 - 20 × height ÷ waist, plus 12 for women, built on DXA scans of 12,581 US adults. The US Navy method uses your neck and abdomen (men) or neck, waist and hips (women), and was developed in US Navy sailors in 1984.
In independent tests, both formulas were typically 4 to 5 percentage points out for one person, and sometimes 10 or more. Both tend to read high in lean people, and the Navy method low in people with more body fat.
No NICE, NHS or WHO guideline sets one, and researchers say there's no consensus. The widely shared ranges were translated from body mass index (BMI) cut-offs, so the calculator doesn't label your result healthy or unhealthy.
Against a laboratory method, 15 devices were on average anywhere from 3.5 points low to 11.7 points high, and three smart scales were judged not accurate. NICE says not to use them in place of BMI.
That's what NICE uses, measured midway between your lowest rib and the top of your hip bone. High body fat on a scan is linked with higher mortality, but home estimates are too rough to judge it.
The small current from a body fat scale interfered with some pacemakers and implanted defibrillators in a pilot study. A tape measure is safe; check with your cardiac team before using a scale's body fat mode.
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As published: "64 - (20 × height/waist circumference) + (12 × sex)", with sex 0 for men and 1 for women. So it's 64 - 20 × height ÷ waist for men and 76 - 20 × height ÷ waist for women, with height and waist in the same units. Woolcott and Bergman picked it from 365 formulas tested against DXA scans of 12,581 US adults aged 20 to 85, and checked it in 3,456 more aged 20 to 69.
Their waist was measured "at the level of the uppermost lateral border of the right ilium", the top of your hip bone, at the end of a breath out. That's lower than NICE's midpoint, so the calculator asks for your waist at the top of your hip bone.
Developed by Hodgdon and Beckett in 1984. In inches, as two studies of the US Army and Marine Corps print them:
The calculator converts centimetres to inches (÷ 2.54) and uses the formulas above for both kinds of units, so you get the same answer either way. A centimetre version also circulates, via body density: 495 ÷ (1.0324 - 0.19077 × log10(waist - neck) + 0.15456 × log10(height)) - 450 for men, and 495 ÷ (1.29579 - 0.35004 × log10(waist + hips - neck) + 0.22100 × log10(height)) - 450 for women. It comes from a different fit and differs by 0.03 to 0.31 points in our test cases (our arithmetic), far less than the method's error.
One study prints the women's formula without the hips, though it measured them: that's a misprint. The Navy method needs your abdomen minus your neck (men), or your waist plus hips minus your neck (women), to be above zero.
Use a tape that doesn't stretch, keep it level and snug without pressing in, and measure after a normal breath out, as WHO's waist protocol does. Each formula has its own sites:
Readings differ by site: in one study of women, the narrowest point gave the smallest reading and just above the hip bone the largest, so use each formula's own site, and the same one each time. For NICE's waist-to-height ratio, measure midway between your lowest rib and the top of your hip bone instead.
Each estimate is shown to the nearest whole percent, with a range 5 points either side:
Each estimate to the nearest whole percent, with "likely within about 5 points either way: roughly X% to Y%". Choose both formulas and you see both, with the gap between them: for the man above, if his waist measured 90 cm at both sites, 24% and 20%, 4 points apart (our arithmetic). An estimate below 2% or above 60% isn't shown: instead you see that it's outside the range these formulas were built for, and a prompt to check your measurements.
There are no healthy or unhealthy bands. The result says "There's no agreed healthy body fat range: no NICE, NHS or WHO guideline sets one", then that for health risk, NICE uses your waist-to-height ratio, measured midway between your lowest rib and the top of your hip bone, with a link to that calculator. It doesn't work out NICE's band from your relative fat mass waist, because that's measured at a different site. Every result ends with where to get support with eating or body worries.
Relative fat mass came from DXA scans of 12,581 US adults in a national survey and was checked in 3,456 more, with median errors of 0.9 points in women and 0.5 in men. The Navy method was "developed against a sample of male and female sailors and validated against a large sample of male and female soldiers" and went on to become the US military's standard, with a standard error of 3 to 4 points.
Against a five-compartment model in 78 adults, relative fat mass read 6.5 points high on average, with 95% of people between 3.0 points low and 16.0 points high. Against DXA it overestimated both sexes in 65 working adults, was less accurate for the number than for flagging high body fat in 270 Chilean adults, and matched DXA in older women with obesity.
The Navy method read 2.5 to 2.6 points low in 430 male Marines and 1.3 to 2.3 points high in 179 female Marines, with standard deviations of 3.7 to 4.8, and 6 points low in 1,407 Army recruits. Its total error was 5.2 points in 31 college men. In 62 women aged 40 to 60 its average was close to underwater weighing (30.3% against 29.5%), but individual results agreed poorly. Lean people were overestimated and people with more fat underestimated.
New formulas built from DXA scans of 1,904 US soldiers improved on the Army's version of the Navy method, more for men than for women. The Army has since moved to a formula using a single waist measurement and weight; against laboratory methods it read 1.3 points high on average, with limits of about 9.5 points either way. Neither is offered here, because both were built for military fitness standards (our choice).
"To date, there is no consensus for the definition of obesity based on body fat percentage" (2018). "There is no established criterion for % fat and health risk" (2007). In 2000, "no accepted published ranges of percentage body fat currently exist". NICE classes people by BMI and the waist-to-height ratio, not body fat.
Fifteen devices gave consistent readings, but their average errors against a four-compartment model ran from 3.5 points low to 11.7 points high. They tracked change over 12 to 16 weeks better. Three smart scales underestimated fat mass by a median of 2.2 to 4.4 kg against DXA and were judged "not accurate for body composition". NICE says not to use bioimpedance as a substitute for BMI.
In 54,420 adults aged 40 and over who had DXA scans, high body fat and low BMI were each linked with higher death rates. BMI misses many people with high body fat, but home estimates are several points out, so NICE uses the waist-to-height ratio for everyday use.
Where the tape goes, since each formula was built on its own sites. For scales, your hydration: European nutrition guidance doesn't recommend them routinely with abnormal hydration or at the extremes of BMI. Even the reference scan has limits: against a four-compartment model, DXA reads low in lean people and men and high at higher body fat and in women.
NICE classes people by BMI and the waist-to-height ratio and says "Do not use bioimpedance as a substitute for BMI as a measure of general adiposity in adults." We found no NHS or WHO body fat ranges either. Researchers have said so plainly for 25 years: "no accepted published ranges of percentage body fat currently exist" (2000), "there is no established criterion for % fat and health risk" (2007), and "to date, there is no consensus" (2018).
Many online charts trace back to a 2000 study. It measured body fat in 1,626 adults of white, African American and Asian background in the UK, US and Japan, fitted formulas predicting body fat from BMI, sex, age and ethnic group (standard errors of 2.8 to 5.4 points), and fed the BMI cut-offs of 18.5, 25 and 30 into them to make "provisional" ranges. Those ranges are BMI cut-offs translated into body fat, not new evidence about health.
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One study used more than 25% for men and more than 35% for women as "the World Health Organization reference standard for obesity"; another calls the same figures "arbitrarily proposed". Charts that sort body fat into "essential", "athletes", "fitness" and "average" come from fitness organisations, not health guidelines (our reading).
WHO notes that "the percentage of body fat mass increases with age up to 60-65 years in both sexes, and is higher in women than in men of equivalent BMI". So any single range would mean something different for a young man than for an older woman.
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A 2025 Lancet commission accepts "direct fat mass measurement (eg, by DEXA or bioimpedance)" to confirm excess body fat, using "validated methods and cutoff points appropriate to age, sex, and ethnicity". Its suggested cut-offs sit in an appendix, to be matched to age, sex and ethnic group or country.
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NICE uses your waist-to-height ratio, measured midway between your lowest rib and the top of your hip bone: keep your waist to less than half your height. The waist-to-height ratio calculator does the sum.
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Cheap and repeatable, and typically 4 to 5 points out for one person against a scan. The formulas lean the wrong way at the extremes: high for lean people, and (for the Navy method) low for people with more body fat.
They send a small current through your body. In 73 adults, 15 devices gave very consistent readings, but their average errors against a four-compartment model ran from 3.5 points low to 11.7 points high, with standard errors of 3.1 to 7.5 points. Over 12 to 16 weeks, the better devices, especially those with hand and foot contacts, tracked change more closely. Three smart scales underestimated fat mass by a median of 2.2 to 4.4 kg against DXA.
NICE: "Do not use bioimpedance as a substitute for BMI as a measure of general adiposity in adults." The European Society for Clinical Nutrition and Metabolism (ESPEN) says bioimpedance "works well in healthy subjects" with a validated equation, but "Clinical use of BIA in subjects at extremes of BMI ranges or with abnormal hydration cannot be recommended for routine assessment", and that the method "suffers from a lack of standardized method and quality control procedures". If you use one, weigh at the same time of day in the same state (our suggestion).
The reference most studies use, but not perfect: against a four-compartment model, DXA reads low in lean people and men and high at higher body fat and in women. A research-grade bioimpedance machine came within 1.4 points of DXA on average in Marines, closer than the tape.
Callipers pinch the fat under the skin at set sites. Against a five-compartment model, a standard skinfold formula was 1.0 point low on average, but individual results ranged from about 12 points low to 10 points high. They need a trained measurer, so this calculator doesn't offer them (our choice).
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Some formulas estimate body fat from BMI, age and sex: one, from a Spanish clinic, had a standard error of 4.66 points in 6,510 adults. But they can't tell muscle from fat, so they're least accurate for muscular people. In US survey data, relative fat mass was better than these formulas at flagging high body fat in men, and similar in women.
In a pilot study of 27 people with pacemakers or implanted defibrillators, the current from a body fat scale or watch caused interference in 5 whose devices were set to their most sensitive, and in none after the settings were adjusted. Don't use a scale's body fat mode unless your cardiac team says it's fine (our suggestion); a tape measure is safe.
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Both formulas were built in adults, so the calculator stops if you enter an age under 18. Children's growth is judged on BMI centiles; our BMI calculator links the NHS calculator for children and teenagers.
Your waist and hips change as pregnancy progresses, so these formulas don't apply (our reading). Ask your midwife about weight in pregnancy.
Body fat numbers can feed worries about food and shape. See a GP, or contact Beat: the support section below has the numbers.
If you measure, weigh or check your body often and it causes you distress, a body fat number won't settle it. The support section below covers what to do.
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The formulas are least accurate at the extremes: they tend to read high in lean people, and the Navy method low in people with more body fat. Treat the number as rough.
Swelling or fluid in the abdomen (ascites), for example with heart, kidney or liver disease, enlarges the waist with fluid, not fat. Ask your care team instead.
This calculator only uses a tape measure. If you also use a body fat scale, check with your cardiac team first.
Source 11
No NICE, NHS or WHO guideline sets one, and researchers say "there is no consensus". The ranges online are translated from BMI cut-offs or come from fitness organisations.
Against a laboratory method, 15 devices were on average anywhere from 3.5 points low to 11.7 points high, and three smart scales were "not accurate for body composition". NICE says not to use them in place of BMI.
It was typically 2 to 6 points out on average in military groups, with a standard deviation of about 4, overestimating lean people and underestimating those with more fat. Relative fat mass did about as well.
It's the best widely available test, but against a four-compartment model it reads low in lean people and men and high at higher body fat and in women.
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Formulas exist (one had a standard error of 4.66 points), but they rely on BMI, which can't tell muscle from fat and misses many people with high body fat.
In 54,420 adults who had scans, a low BMI was linked with higher mortality, separately from body fat. Very low body weight isn't a health goal: if you're losing weight without trying, see a GP.
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If you have, or think you might have, an eating disorder, these numbers aren't the right tool: the NHS calculators say the same. Eating disorders can affect people at any weight. 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), or email help@beateatingdisorders.org.uk (Scotland, Wales and Northern Ireland have their own addresses on Beat's website, along with opening times). If you or someone else is in immediate danger, call 999 or Samaritans on 116 123; for medical advice, call 111.
The NHS lists these among the signs of an eating disorder:
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The NHS lists worrying "a lot about a specific area of your body", spending "a lot of time comparing your looks with other people's" and looking "at yourself in mirrors a lot" among the signs of body dysmorphic disorder (BDD). "You should see a GP if you think you might have BDD", and you can also refer yourself to an NHS talking therapies service.
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If numbers like these 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).
Strength training builds muscle, and with cardio it changes your body more than the scales show. Start with the 20-minute or bodyweight sessions, then move to the dumbbell or gym workouts.
A 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 20-minute full-body workout with no equipment: squats, knee push-ups, bridges, lunges and planks.
20 minBeginner10 movesNo equipmentA 35-minute full-body strength workout with dumbbells: goblet squats, presses, rows, Romanian deadlifts and carries.
35 minIntermediate9 movesA band, A dumbbellA beginner full-body gym workout: goblet squats, dumbbell bench press, lat pulldowns, Romanian deadlifts and dead bugs, with sets, reps and rest.
45 minBeginner12 movesCardio machine, A bandA 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 wallWith a tape measure: relative fat mass uses your height and your waist at the top of your hip bone, and the US Navy method uses your height, neck and waist, plus hips for women. Body fat scales are quicker but less accurate. Either way, expect to be several points out.
In military groups it was typically 2 to 6 points out on average against DXA, with individual errors of about 4 points either way. It overestimates lean people and underestimates people with more body fat, so the calculator shows a range of 5 points either side of your estimate.
A 2018 formula: 64 minus 20 × your height ÷ your waist, plus 12 for women, built on DXA scans of 12,581 US adults. It uses the same two measurements as the waist-to-height ratio, but with the waist taken at the top of your hip bone, so it isn't the same as NICE's ratio.
There's no agreed answer: no NICE, NHS or WHO guideline sets one, and researchers say there's no consensus. Ranges online mostly come from fitness organisations or from BMI cut-offs translated into body fat. For health risk, NICE uses your waist-to-height ratio, measured midway between your lowest rib and the top of your hip bone.
They're consistent from day to day, but in tests against laboratory methods their averages were up to about 12 points out, and three smart scales were judged not accurate. They're better for tracking a trend than for a single number. If you have a pacemaker or implanted defibrillator, check with your cardiac team before using one.
Each formula uses different measurements, was built in different people, and depends on exactly where the tape goes. For the same man in our example, relative fat mass gives 24% and the Navy method 20%, both within each other's error.
You can estimate it, but formulas based on BMI can't tell muscle from fat, so they're least accurate for muscular people. A tape measure round your waist adds the most useful extra information.
Body fat measured by a scan picks up health risks that BMI misses. But home estimates are several points out, so for everyday use the waist-to-height ratio is the measure NICE uses.
Measure your neck just below the Adam's apple. Men measure the abdomen level with the navel; women measure the waist at its narrowest and the hips at their widest. Keep the tape level and snug, and measure after a normal breath out.
On average, yes: at the same BMI, body fat rises with age to about 60 to 65, and it's higher in women than in men. That's one reason BMI alone can mislead.
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.
