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BMR Calculator

Basal metabolic rate: the calories you burn doing nothing at all.

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What the three formulas predict

Basal metabolic rate

—

Calories burned at complete rest, per day.

With activity added

Sedentary (×1.2)—
Lightly active (×1.375)—
Moderately active (×1.55)—
Very active (×1.725)—
Extremely active (×1.9)—

A population estimate, not a measurement. Individual metabolic rates vary considerably, and only indirect calorimetry measures yours directly. Treat this as a starting point rather than a target.

Quick Tool Overview

The BMR Calculator estimates your basal metabolic rate — the energy your body uses at complete rest to run your heart, brain, lungs and other organs. Three formulas are calculated together so you can see the spread between them.

What it does
Estimates basal metabolic rate by three different formulas
You give it
Age, sex, height, weight and optionally body fat
You get back
Three BMR estimates side by side
Best for
Understanding your baseline before setting a calorie target
Calculators Free, unlimited use No sign-up Runs in your browser

About the BMR Calculator

Basal metabolic rate is the energy your body uses at complete rest to run your heart, brain, lungs and other organs. It is the largest single component of daily expenditure for most people, typically between 60 and 75 percent of the total.

Three formulas are calculated together so you can see the spread: Mifflin-St Jeor, the modern default; Harris-Benedict, the older revision still widely quoted; and Katch-McArdle, which uses lean body mass instead of total weight and is the most accurate of the three if you know your body fat percentage. Comparing them is instructive, since a hundred-calorie disagreement between formulas is normal and a useful reminder of how approximate any of them are.

Key features of the BMR Calculator

Three formulas compared

Mifflin-St Jeor as the modern default, Harris-Benedict as the older revision still widely quoted, and Katch-McArdle for when you know your body fat.

Katch-McArdle uses lean mass

The most accurate of the three if you have a body fat percentage, because it works from lean body mass rather than total weight.

The spread is instructive

A hundred-calorie disagreement between formulas is normal, and a useful reminder of how approximate any of them are.

Context for the number

BMR is typically 60 to 75 percent of total daily expenditure, which the page states rather than leaving you to guess.

Private and instant

Measurements are used in your browser and never sent anywhere.

How to use the BMR Calculator

  1. 1

    Enter your measurements

    Age, sex, height and weight in metric or imperial units.

  2. 2

    Add body fat if you know it

    Optional, but it enables the Katch-McArdle formula, which is the most accurate when lean mass is known.

  3. 3

    Compare the formulas

    All three estimates are shown together, along with the difference between them.

Frequently asked questions

BMR is what you burn at complete rest. Total daily energy expenditure is BMR multiplied by an activity factor, so it includes movement, exercise and digesting food.

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