BMR calculator
Your basal metabolic rate (BMR) is the number of calories your body burns at complete rest, just to keep you alive. FitCalcs works it out with the Mifflin-St Jeor equation, the formula UK dietitians use, and offers the Cunningham equation if you know your body-fat percentage. BMR is the starting point for your full daily calorie burn: multiply it by an activity factor to get your TDEE. This is general information, not personalised dietary advice.
How this is worked out
Mifflin-St Jeor is the resting-metabolism equation UK dietitians and the British Dietetic Association use as standard:
BMR = (10 x weight kg) + (6.25 x height cm) − (5 x age) + s
s = +5 for men, −161 for women
Cunningham is preferred when you know your lean body mass, because it tracks muscle directly. It tends to read higher than Mifflin-St Jeor for lean, muscular people:
BMR = 500 + (22 x lean mass kg)
lean mass = weight x (1 − body-fat % / 100)
Informational only, not medical or dietary advice. BMR is calories burned fully at rest. Editorially reviewed by FitCalcs, with each figure citing its source.
Common questions
What is BMR and how is it calculated?
Your basal metabolic rate is the calories your body burns at complete rest just to stay alive, before any movement. FitCalcs works it out with the Mifflin-St Jeor equation, the formula UK dietitians generally use, from your age, sex, height and weight. This is general information, not personalised dietary advice.
What is the Mifflin-St Jeor equation?
It is the BMR formula most clinicians rely on. For men, BMR = (10 times weight in kg) + (6.25 times height in cm) minus (5 times age) plus 5. For women it is the same sum but minus 161 at the end. Published in 1990, it tends to estimate resting energy needs more accurately than older equations for most healthy adults.
What is the difference between BMR and TDEE?
BMR is what you burn at rest; TDEE is everything you burn in a full day. Your total daily energy expenditure (TDEE) is your BMR multiplied by an activity factor, from 1.2 if you are sedentary up to 1.9 if you are extremely active. BMR is the starting point, and the activity factor accounts for movement, exercise and daily living.
When would I use the Cunningham equation instead?
Use Cunningham if you know your body-fat percentage, because it works from your lean body mass rather than total weight. That makes it a better fit for lean, muscular people, whose muscle raises their resting burn above what a height-and-weight formula predicts. If you do not know your body fat, Mifflin-St Jeor is the sensible default.
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Editor, FitCalcs
Oliver Mackman is the named editor of FitCalcs and a director of Best Business Loans Ltd (Companies House 16833937), the company that operates the site. He is accountable for its editorial standards, sourcing and corrections, and requires every result to cite the underlying equation and the named UK source behind it, with health tools carrying the appropriate not-medical-advice caveats.
Last reviewed: 12 June 2026