BMR Calculator
Estimate your basal metabolic rate — the energy your body uses at complete rest — with the Mifflin-St Jeor equation, and compare it with Harris–Benedict.
The calories your body burns just staying alive, before any activity.
How the bmr calculator works
Basal metabolic rate is the energy needed to keep you alive at rest: breathing, circulation, cell repair, temperature. The Mifflin-St Jeor equation (1990) predicts it from weight, height, age and sex and is the one most dietitians use today because it fits measured values better than the older Harris–Benedict equation (1919, revised 1984), which is shown alongside for comparison.
BMR is not a calorie target. Multiply it by an activity factor to get total daily energy expenditure — the TDEE calculator does that — and remember that any equation predicts the average person of your size; individuals vary by around 10%.
Formula: Men: BMR = 10W + 6.25H − 5A + 5 · Women: BMR = 10W + 6.25H − 5A − 161 (W kg, H cm, A years)
Worked examples
| Inputs | BMR (Mifflin-St Jeor) | Note |
|---|---|---|
| Man, 30, 175 cm, 75 kg | 1,699 kcal/day | 10×75 + 6.25×175 − 5×30 + 5 |
| Woman, 45, 162 cm, 60 kg | 1,227 kcal/day | the −161 constant applies |
| Man, 25, 6 ft 1 in, 190 lb | 1,901 kcal/day | converted to 185.4 cm and 86.2 kg first |
| Woman, 68, 158 cm, 70 kg | 1,187 kcal/day | BMR falls about 5 kcal a day per year of age |
FAQFrequently asked questions
What is BMR?
Basal metabolic rate is the energy your body needs at complete rest to run its basic functions — breathing, blood flow, cell repair, keeping warm. It is usually 60–70% of everything you burn in a day.
Mifflin-St Jeor or Harris–Benedict — which should I use?
Mifflin-St Jeor. Validation studies find it within 10% of measured resting energy expenditure more often than Harris–Benedict, which tends to run a little high. Both are shown so you can see how close they are for you.
Is my BMR the number of calories I should eat?
No. BMR is the floor. Eating at BMR ignores every step you take. Multiply by an activity factor (the TDEE calculator does this) to find maintenance calories, then adjust for a goal.
Why does my result differ from a smart scale or a lab test?
Equations predict the average person of your height, weight, age and sex. Muscle mass, genetics, thyroid function and medication move the true figure by 10% or more either way. Indirect calorimetry in a lab is the only direct measurement.
Where these figures come from
- Mifflin MD et al., "A new predictive equation for resting energy expenditure in healthy individuals", Am J Clin Nutr 1990 — the BMR equation used here
- World Health Organization — Waist circumference and waist–hip ratio (2008 expert consultation) — waist-to-hip cut-offs
- Tanaka H, Monahan KD, Seals DR, "Age-predicted maximal heart rate revisited", J Am Coll Cardiol 2001 — 208 − 0.7 × age
- Nathan DM et al., "Translating the A1C assay into estimated average glucose values" (ADAG), Diabetes Care 2008 — eAG = 28.7 × A1c − 46.7
- Mosteller RD, "Simplified calculation of body-surface area", N Engl J Med 1987 — BSA = √(height × weight / 3600)
- Australian Department of Health and Aged Care — national health guidance
Last checked: September 2026. The equations are fixed by their published papers and do not change with tax years or regulations; the thresholds quoted in verdicts name the body that set them.