Ten calculators that show their working. Each one tells you which formula it uses and why, how far out it can be for one person, and when a number isn't the right tool, such as heart rate targets on a beta blocker or BMI in pregnancy.
Each sits on top of a guide to the evidence, with links to the workouts and plans that use the result. They're estimates for healthy adults, and they don't replace advice from your GP or care team.
Each page names its formula and its source, and the body, food and running pages do the same with NICE's bands, the energy equations and the race models they use. The one-rep max is the average of the Epley and Brzycki formulas, with five more alongside. Maximum heart rate starts from 208 minus 0.7 times your age, with three other formulas to choose from, and heart rate reserve (the Karvonen method) if you know your resting heart rate. Calories are MET (metabolic equivalent) values from the 2024 Compendium of Physical Activities × your weight × the time, with older-adult values for over-60s.
A one-rep max estimate is usually close but can be 10% or more out. An age formula can put your maximum heart rate about 10 beats out, and 20 or more for some people. Calorie values are averages, so two people on the same walk can burn noticeably different amounts, and watches are often further out.
On a beta blocker or another medicine that slows your heart, heart rate zones won't fit: use the talk test and how hard it feels. In pregnancy, resting heart rate rises by about 10 to 20 beats, so guidance uses effort instead. And many people shouldn't test a true one-rep max at all, including beginners, people with uncontrolled blood pressure or heart disease, and older people new to lifting.
The calories calculator doesn't turn calories into weight. Exercise alone takes off about 2 to 3 kg on average, because the body makes up some of what you burn, and the 3,500-calories-per-pound rule overestimates weight loss.
Good enough to start from, not exact. A one-rep max estimate is usually close but can be 10% or more out for one person, an age-based maximum heart rate can be about 10 beats out, and 20 or more for some, and calorie values are averages that can be noticeably off for you. Each calculator says how far out its numbers can be.
Which formulas do these calculators use?
Each page writes out its formula and its source. BMI and the waist-to-height ratio use NICE's bands, calories a day come from the Mifflin-St Jeor equation times a measured activity level, and protein follows guideline grams per kg. The one-rep max averages the Epley and Brzycki formulas, maximum heart rate starts from 208 minus 0.7 times your age, calories burned use the 2024 Compendium, and race predictions use Riegel's formula, with a mileage model for the marathon.
Do I need to test my one-rep max?
No. A set of 3 to 10 reps, with a note of how many more you could have done, gives a good estimate, and you don't need a true max to train well. Testing one isn't advised if you're new to lifting, pregnant, recovering from heart or hernia surgery, or have uncontrolled blood pressure, heart disease or diabetic eye disease.
Can I use heart rate zones if I take a beta blocker or I'm pregnant?
Not reliably. Beta blockers and some other heart medicines slow your heart, so zones from a formula won't fit, and in pregnancy your resting heart rate rises. Use the talk test and how hard it feels instead, and follow any target your care team gives you; the heart rate calculator puts this first when you tick either box.
Can I turn calories burned into kilos lost?
Not reliably, so the calories calculator doesn't. The body makes up some of the energy you burn, through appetite and a slightly lower resting burn, and exercise alone takes off about 2 to 3 kg on average. Use the calories to compare activities, and see our exercise for weight loss guide for what exercise does well.
What should I do with my results?
Use them as starting points. Pick training weights from the one-rep max table and adjust them by how many reps you have left, use the heart rate zones as a guide and let the talk test decide, and use calories to compare activities rather than to plan meals. Our workout plans show how to build them into a week.
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.