BMR Calculator (Basal Metabolic Rate)

Enter your sex, age, height, and weight to calculate your Basal Metabolic Rate (BMR) — the minimum energy your body burns at rest — using both the original 1919 and revised 1984 Harris-Benedict equations, side by side.

Last updated: 2026-09-20

What basal metabolic rate (BMR) is

Basal metabolic rate (BMR) is the amount of energy your body burns automatically for the business of staying alive — breathing, holding its temperature, beating the heart, repairing cells — even on a day spent entirely at rest. It excludes whatever you spend moving about on exercise or housework, so it is rather like the standby power needed to keep the machine that is your body minimally running.

This tool estimates BMR from four items — sex, age, height and weight — using the Harris-Benedict equation. It works out both the original published in 1919 and the revision in which Roza and Shizgal reworked the coefficients in 1984, and shows them side by side, so you can see at a glance how much the two equations differ.

Reference figures used in this calculation

The figures below are not set by law. They are reference values used as a guide, and the actual amounts differ from provider to provider.

Health and body-composition estimation formulas (BMR, body fat, one-rep max, growth indices and so on) — Estimation formulas from published research (not an official standard) （No unified official dataset exists） Last checked 2026-09-21

How we source and maintain these figures

How to calculate basal metabolic rate

Choose your sex Because differences in body composition give men and women different coefficients, start by choosing one or the other.
Enter your age Age works to lower basal metabolism, so within the equation it is handled as a negative coefficient.
Enter your height Give it in centimetres. It serves as a proxy for body surface area, and the larger the figure the higher the BMR.
Enter your weight Give it in kilograms. Of the four inputs, this is the one with the greatest bearing on BMR.
Compare the two results The BMR from the original and from the revision, along with the difference between them, appear automatically.

Tips for getting more out of it

BMR is the energy your body burns just to stay alive at complete rest — breathing, maintaining body temperature, and running your organs. It does not include any activity or exercise.
To estimate your total daily energy expenditure (TDEE), multiply this BMR value by an activity multiplier — roughly 1.2–1.375 for a mostly sedentary desk job, or 1.55 or higher if you exercise regularly.
It is normal for the two formulas to give slightly different numbers. The 1984 revision is based on newer body-composition data than the 1919 original, so it is usually considered closer to reality.
People with unusually high or low muscle mass (athletes, older adults) may find that this height/weight/age-based formula diverges noticeably from their actual BMR.

When basal metabolic rate is useful

Making it the starting point of a diet plan

When thinking about calorie intake, knowing your BMR first gives you a baseline for checking that you have not ended up eating far too little.

Preparing to estimate your daily total burn

Add your everyday activity to BMR and you get a guide to the calories you actually burn in a day, your TDEE. The calculation including activity level can be done with a total calorie expenditure tool.

Setting the pace for gaining or losing

Depending on whether you want to build muscle or reduce body fat, it gives you the material for considering how far to move your intake above or below your BMR.

Grasping how metabolism differs by age and sex

Run the calculation a few times with different ages and sexes and you get a feel for how much metabolism shifts at the same build.

Basal metabolic rate terms

Basal metabolic rate (BMR): The minimum energy needed to sustain life, burned even while resting. It is held to make up roughly 60 to 70 percent of the total calories burned in a day.
Harris-Benedict equation: An equation that estimates BMR from sex, age, height and weight. The name usually refers to the original published in 1919, which this tool also calculates.
Revised Harris-Benedict equation (1984): The equation Roza and Shizgal published after reworking the coefficients of the original on the basis of the newer body data of their time. This tool shows its result alongside the original.
Lean body mass: Weight with body fat taken out, comprising muscle, bone and so on. The greater the lean body mass, the higher the BMR tends to be at the same total weight.
Total daily energy expenditure (TDEE): The total calories you actually burn in a day, being BMR plus the energy spent on everyday activity. It is this figure that intake plans for dieting or bulking are based on.
Activity metabolism: The energy burned through physical activity such as exercise, housework and commuting. It is not part of BMR and is added separately when working out TDEE.

FAQ

BMR is the minimum amount of energy your body needs to stay alive — powering your heartbeat, breathing, and body temperature regulation without any physical activity. It typically accounts for about 60–70% of your total daily calorie burn.

It is a formula published in 1919 by American researchers James Arthur Harris and Francis Gano Benedict, which estimates BMR from sex, height, weight, and age. In 1984, Roza and Shizgal revised the coefficients using more current body-composition data.

Men generally carry more muscle mass and lower body fat than women, and muscle burns more energy at rest than fat does. So for the same height, weight, and age, men tend to have a higher BMR — the equations use separate coefficients to reflect this difference in body composition.

Eating well below your total daily energy expenditure (BMR adjusted for activity level) tends to produce weight loss, but cutting calories drastically below your BMR itself can risk muscle loss and a slowed metabolism, so extreme restriction is not recommended.

Side Note — A formula born in a lab a century ago

The roots of the Harris-Benedict equation trace back, surprisingly, to 1919 — right after the end of World War I. At the Carnegie Institution in Washington, D.C., nutrition researchers James Arthur Harris and Francis Gano Benedict measured the respiratory gas exchange (indirect calorimetry) of hundreds of subjects, and statistically derived the relationship between height, weight, age, sex, and energy expenditure.

The formula remained the standard in nutrition and medicine for over six decades, until 1984, when researchers Anne Roza and Shakuntala Shizgal revisited the original coefficients using more current data and published a more accurate revised version. This tool displays both formulas side by side precisely to reflect that history.

In 1990, the Mifflin-St Jeor equation was published, considered a better fit for modern body types than Harris-Benedict, and it is increasingly used in clinical settings today. Even so, Harris-Benedict remains the most widely known BMR formula, and the fact that painstaking lab measurements from a century ago still underpin modern diet and nutrition tracking is one of the more fascinating stories in the history of nutrition science.

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