Your basal metabolic rate (BMR) is the energy your body uses at complete rest to keep you alive: breathing, circulation, temperature and cell repair. It is usually the largest part of daily calorie burn. This calculator uses the Mifflin–St Jeor equation, published in the American Journal of Clinical Nutrition in 1990 from indirect-calorimetry measurements of 498 healthy adults aged 19–78. In that study the older Harris–Benedict equations overestimated measured resting energy expenditure by about 5%.
For a 30-year-old man who is 180 cm (5 ft 11 in) and 80 kg (176 lb), BMR is about 1,780 Calories a day. A woman of the same age, height and weight comes out at about 1,614.
How to use the bmr calculator
- Choose sex and enter age.
- Choose US or metric units and enter height and weight.
- Read your BMR in Calories (kcal) per day. To include activity, multiply by an activity factor in the tdee calculator.
Formula
These are the simplified sex-specific forms given by Mifflin et al. (1990). The combined regression was REE = 9.99 × weight + 6.25 × height − 4.92 × age + 166 × sex (male = 1, female = 0) − 161. US inputs are converted with 1 lb = 0.45359237 kg and 1 in = 2.54 cm.
Worked example
Man, 30 years, 180 cm, 80 kg.
- 10 × 80 = 800.
- 6.25 × 180 = 1,125.
- 5 × 30 = 150.
- BMR = 800 + 1,125 − 150 + 5 = 1,780 Calories/day, about 74 Calories an hour.
For a woman with the same numbers: 800 + 1,125 − 150 − 161 = 1,614 Calories/day.
BMR, RMR and total daily burn
Strictly, BMR is measured after an overnight fast in a lab, while resting metabolic rate (RMR or REE) is measured under less strict conditions. The Mifflin–St Jeor equation predicts REE, and the two are close enough that most calculators use the terms interchangeably. Your total daily energy expenditure adds movement, exercise and the energy used to digest food, typically 1.4 to 2.5 times resting needs according to the NIDDK Body Weight Planner. Use the tdee calculator for that, then the calorie deficit calculator or macro calculator to plan intake.
Fat-free mass was the strongest single predictor in the Mifflin study, so two people with the same weight but different muscle mass can have different real BMRs. If you know your body-fat percentage from the body fat calculator (u.s. navy method), remember that this equation does not use it.
Caveats and assumptions
- Predictive equations estimate an average; an individual’s measured BMR can be 10% or more above or below.
- Developed in healthy adults; it may be less accurate for older adults, athletes, people with obesity, or during illness or pregnancy.
- Not medical or dietary advice. Do not eat below your BMR without professional guidance.
Frequently asked questions
What is a normal BMR?
It depends on weight, height, age and sex, so there is no single normal value. By the Mifflin–St Jeor equation a 30-year-old man at 180 cm and 80 kg is about 1,780 Calories a day, and a woman with the same measurements about 1,614.
Which BMR formula is most accurate?
Mifflin–St Jeor is widely used. In its 1990 validation the older Harris–Benedict equations overestimated measured resting energy expenditure by about 5%.
Is BMR the same as calories burned per day?
No. BMR is calories at rest. Total daily burn (TDEE) adds activity and is typically 1.4 to 2.5 times higher.
Does muscle increase BMR?
Yes. Fat-free mass was the strongest single predictor of resting energy expenditure in the Mifflin study.
Sources
- Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51(2):241-7 (PubMed) — the equation and the 5% Harris–Benedict comparison
- NIDDK — Body Weight Planner — physical activity levels from 1.4 (sedentary) to 2.5 (very active)
- NIST SP 811 Appendix B.9 — Conversion factors — lb→kg and in→cm
This calculator gives general estimates for healthy adults and is not medical advice, diagnosis or treatment. Equations are averages and individuals differ. Talk to a qualified health professional before changing your diet, exercise or medication, and during pregnancy. See our disclaimer and how we build and check calculators.