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

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

Use this BMR calculator to estimate how many calories your body burns at rest, then get a quick Total Daily Energy Expenditure (TDEE) range based on activity level. It’s a practical starting point for calorie planning, weight management, and fitness goals.

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

Enter your details and click Calculate.

About this BMR calculator

Basal Metabolic Rate (BMR) is the energy your body uses just to keep you alive—breathing, circulation, temperature control, and basic organ function. This calculator estimates your resting calorie burn using several trusted equations, then lets you see a quick TDEE estimate by applying an activity multiplier.

How to use it

  1. Enter your sex, age, height, and weight, choosing metric or imperial units.
  2. Add body fat % if you know it for a lean-mass-based estimate.
  3. Select the formulas you want to compare.
  4. Pick your typical activity level to view TDEE estimates.
  5. Use the results as a starting point for daily calorie planning.

When it’s useful

  • Setting a baseline for weight maintenance, fat loss, or muscle gain goals.
  • Comparing different BMR equations to see how estimates vary.
  • Planning meal portions, calorie intake, or training phases.
  • Tracking how changes in weight or body fat affect energy needs.

Formulas in this calculator

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

Equations (optional detail)

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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