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BMR Calculator

Estimate basal metabolic rate — the energy your body uses at complete rest — using the Mifflin-St Jeor equation.

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What BMR Calculator does

Basal metabolic rate is the energy required to keep you alive while doing nothing: circulation, breathing, temperature regulation and cell maintenance. For most people it is the largest single component of daily energy use.

The Mifflin-St Jeor equation, published in 1990, is the estimate most dietitians now use, having been found more accurate for modern populations than the older Harris-Benedict formula.

  • Mifflin-St Jeor estimate from sex, age, height and weight
  • Daily and weekly figures

How to use BMR Calculator

  1. 1

    Enter your details

    Sex, age, height in centimetres and weight in kilograms.

  2. 2

    Read your BMR

    This is energy at complete rest, not your daily requirement. Nobody spends the day at rest.

  3. 3

    Move on to total daily energy

    Use the calorie calculator to apply an activity multiplier and get a usable daily figure.

Example

The equation

Input

Male, 35 years, 180 cm, 80 kg

Output

BMR = (10 × 80) + (6.25 × 180) − (5 × 35) + 5
    = 800 + 1125 − 175 + 5
    = 1755 kcal/day

For women the final term is −161 instead of +5, which is the only difference between the two forms of the equation.

Limits and known behaviour

  • This is a population estimate. Individual metabolic rate varies by roughly ten percent either side of the prediction even among people with identical measurements.
  • The equation uses total body weight and cannot see body composition. Muscle burns more at rest than fat, so it under-predicts for very lean people and over-predicts for those with high body fat.
  • Thyroid conditions, some medications and significant illness alter metabolic rate in ways no formula can capture.
  • The equation is for adults; it is not validated for children.
  • Metric units only.
  • This is an estimate from a published formula, not a medical assessment. It cannot diagnose anything, and it is no substitute for advice from a clinician who knows your history.

Privacy and data handling

Runs entirely in your browser

  • Every figure you enter stays in this page. Your body measurements is not transmitted, logged or stored anywhere.
  • There is no account, no saved history and no autosave: reloading the page clears the form.

Site-wide data handling, including analytics and advertising, is described in the privacy policy.

Frequently asked questions

Is BMR the number of calories I should eat?

No, and eating at BMR would be a substantial deficit for almost anyone. BMR is energy at rest; your daily requirement adds everything you actually do.

Why does Mifflin-St Jeor give a different answer from Harris-Benedict?

They are different equations fitted to different populations. Mifflin-St Jeor was derived from a more recent sample and is generally considered more accurate today, typically predicting slightly lower values.