BMR Calculator — Mifflin–St Jeor, Harris–Benedict, Katch–McArdle & Schofield

Enter your details. All calculations run locally in your browser—nothing is uploaded.

Your details & options

Used by MSJ, Harris-Benedict, Schofield.
Switch between centimeters and feet/inches.
Used for Katch–McArdle (lean body mass).

Formulas

Results are estimates. For medical advice, consult a clinician.

Results

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About the formulas

Basal Metabolic Rate (BMR) estimates how many calories your body burns at rest. This tool computes BMR using multiple research-backed equations:

  • Mifflin–St Jeor (1990): Often most accurate for general use.
  • Harris–Benedict (revised): Classic formula with updated coefficients.
  • Katch–McArdle: Uses lean body mass when body fat % is known.
  • Schofield: Uses age/sex-specific constants (commonly used by WHO/FAO).

Equations

Mifflin–St Jeor (men): \( \mathrm{BMR} = 10w + 6.25h - 5a + 5 \)
Mifflin–St Jeor (women): \( \mathrm{BMR} = 10w + 6.25h - 5a - 161 \)

Harris–Benedict (revised) (men): \( \mathrm{BMR} = 88.362 + 13.397w + 4.799h - 5.677a \)
Harris–Benedict (revised) (women): \( \mathrm{BMR} = 447.593 + 9.247w + 3.098h - 4.330a \)

Katch–McArdle: \( \mathrm{BMR} = 370 + 21.6 \times \mathrm{LBM} \), where \( \mathrm{LBM} = w \times (1 - \mathrm{bf}) \)

Schofield: \( \mathrm{BMR} = A \times w + B \) (A and B depend on age group & sex).

Here \(w\) is weight in kg, \(h\) is height in cm, \(a\) is age in years, and \(\mathrm{bf}\) is body fat fraction.

Frequently Asked Questions

Which formula should I use?

Mifflin–St Jeor is a solid default. If you know body fat %, Katch–McArdle personalizes the estimate using lean mass.

How do you compute TDEE?

TDEE = BMR × activity factor. We show a quick table using standard multipliers.

Is my data private?

Yes—everything runs locally in your browser. No uploads or storage.

5 Fun Facts about BMR

100-year formula

The Harris–Benedict equation first appeared in 1918; it was refreshed in 1984, then challenged by Mifflin–St Jeor in 1990 for better modern accuracy.

History

Lean-mass purist

Katch–McArdle ignores age and sex; it only cares about lean body mass. Add muscle and it bumps your estimate linearly.

Muscle-first

Organs are power-hungry

Your liver, brain, heart, and kidneys weigh only ~5% of you but burn roughly half of your resting calories.

Tiny engines

Silent majority of calories

For desk-bound adults, BMR often covers 60–75% of daily burn—most calories go to “keeping the lights on,” not workouts.

Daily pie

Sleep debt effect

Small studies show a single short night (4–5 hours) can nudge next-morning resting energy down a few percent—your body eases off when under-rested.

Rest matters

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