BMR Calculator
Estimates adult resting energy (BMR/REE) with the Mifflin–St Jeor (1990) or revised Harris–Benedict (1984) equation, in kcal and kJ per day, both shown side by side — a population prediction, not a calorie target.
Inputs
Estimated resting energy (BMR/REE) for adults by Mifflin–St Jeor (1990) or revised Harris–Benedict (1984), in kcal and kJ per day, with both shown side by side.
Enter the values and press Calculate.
Or load an example to see a worked result.
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Choose the equation and the coefficient set (the published equation has separate male and female constants).
- Enter age (18–100), height in cm or inches and weight in kg or pounds.
- Press Calculate to see the estimate in kcal/day and kJ/day, the substituted equation and the formula comparison.
How it works
Mifflin–St Jeor (1990): REE = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5 for the male coefficients, or − 161 for the female coefficients. kJ/day = kcal/day × 4.184.
It predicts the average for people like you; it is not a measured basal metabolism, not total daily energy use (TDEE) and not a minimum safe intake or a target. No confidence interval is invented.
Revised Harris–Benedict (Roza & Shizgal 1984): 88.362 + 13.397 × weight + 4.799 × height − 5.677 × age (male coefficients), or 447.593 + 9.247 × weight + 3.098 × height − 4.330 × age (female coefficients). The coefficients are taken from the Dutch national clinical guideline table that reproduces the 1984 paper; the paper itself sits behind a publisher paywall, and the page says so beside the result. Adults only, and not validated here for pregnancy, breastfeeding or acute illness. Your inputs are not put in the page address or saved.
Worked example
80 kg, 180 cm, 30 years. Mifflin–St Jeor, male coefficients: 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1125 − 150 + 5 = 1,780 kcal/day (≈ 7,448 kJ/day); female coefficients: the same terms − 161 = 1,614 kcal/day. Revised Harris–Benedict for the same inputs: 88.362 + 1,071.76 + 863.82 − 170.31 = 1,854 kcal/day (male) and 1,615 kcal/day (female) — the two equations differ by 74 kcal/day for the male set.
Tips
- Estimate only — not medical or nutritional advice. Individual needs vary.
Frequently asked questions
Why do BMR formulas give different answers?
Each equation was fitted to a different group of people and era, so the coefficients differ and results can disagree by tens to hundreds of kcal. None is exact for an individual — this tool shows Mifflin–St Jeor and revised Harris–Benedict side by side so you can see how far they disagree for your inputs.
Is BMR a calorie intake target?
No. It estimates energy used at complete rest. It is not a minimum safe intake, a weight-loss target or a prescription — ask a health professional for personal advice.
What is the difference between BMR and TDEE?
BMR (or REE) is resting energy only. TDEE adds the energy of activity and digestion; use the TDEE calculator for that, which is a separate estimate.
Privacy?
Runs entirely in your browser. Your inputs are not saved or transmitted.
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Cite this tool
Zerdly. (2026). BMR Calculator. Retrieved from https://www.zerdly.com/tools/bmr-calculator/
Tip: Enter any known values to calculate the remaining results.
Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.