BMR Calculator

About this free bmr calculator tool

Estimate basal metabolic rate with the Mifflin–St Jeor equation. Calculators answer a defined arithmetic question using the values you supply. Keep units and currencies consistent, choose the correct starting amount and inspect the assumptions before using a result. Estimates do not replace a lender quotation, an official tax rate, a medical assessment or a jurisdiction-specific deadline rule.

How do you calculate your basal metabolic rate?

Basal metabolic rate describes the energy the body uses at rest to support basic functions such as breathing, circulation and temperature regulation. A BMR calculator estimates this energy from body measurements rather than measuring oxygen consumption in a laboratory. The Mifflin–St Jeor equation uses weight in kilograms, height in centimeters, age in years and a sex-specific constant.

The equation gives an estimate in kilocalories per day, often called calories on food labels. It does not include the full energy cost of walking, work, exercise or digesting food, so it is not the same as a daily calorie allowance. Actual resting energy use varies with body composition, health and other factors. The equation’s male and female constants reflect its original model, not every individual’s physiology. Use the estimate for general planning, not as a prescribed intake or a substitute for clinical guidance.

BMR = 10W + 6.25H − 5A + s; W = kg, H = cm, A = years; s = 5 for male or −161 for female.

A worked example

Using the male constant for a 30-year-old weighing 70 kg at 175 cm gives 700 + 1,093.75 − 150 + 5. Estimated BMR is 1,648.75 kcal per day.

Common mistakes to avoid

• Entering height in meters instead of centimeters changes the estimate substantially.
• Treating BMR as total daily calorie needs leaves out activity.
• Interpreting a population-based equation as an exact personal measurement creates false precision.

Frequently asked questions