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BMR Calculator

Calculate your Basal Metabolic Rate using multiple formulas

BMR Calculator Guide: Calculate Basal Metabolic Rate for Weight Management

A BMR calculator estimates your Basal Metabolic Rate—the calories needed at complete rest. The tool supports Mifflin–St Jeor, Harris–Benedict (revised), and Katch–McArdle formulas and converts BMR to daily calories (TDEE) using an activity multiplier.

What is BMR Calculator?

The BMR calculator helps plan nutrition by estimating resting energy needs and scaling them to daily living and training loads. It’s useful for weight management, athletic programming, and clinical screening.

How to Use the BMR Calculator

  1. Enter sex, age, height, weight (and body fat % if using Katch–McArdle).
  2. Choose the formula (Mifflin–St Jeor default).
  3. Select activity level to compute TDEE.
  4. Optionally set a goal (deficit/surplus) to estimate target calories.
  5. Review outputs: BMR, TDEE, and macro suggestions (if provided).

Formulas & Methods

  • Mifflin–St Jeor (kcal/day):
    • Men: BMR = 10·W + 6.25·H − 5·A + 5
    • Women: BMR = 10·W + 6.25·H − 5·A − 161
      (W in kg, H in cm, A in years)
  • Harris–Benedict (revised 1984/1990):
    • Men: BMR = 13.397·W + 4.799·H − 5.677·A + 88.362
    • Women: BMR = 9.247·W + 3.098·H − 4.330·A + 447.593
  • Katch–McArdle (uses lean mass): BMR = 370 + 21.6·LBM, with LBM = W × (1 − bodyfat%).

Activity factors (typical):
Sedentary ×1.2, Light ×1.375, Moderate ×1.55, Very ×1.725, Extra ×1.9 → TDEE = BMR × factor.

Assumptions & limitations

  • Predictive equations give estimates; individual variance is normal.
  • BMR/TDEE shift with lean mass, illness, thermic effect of food, and NEAT.
  • Use clinical guidance for medical conditions.

Examples

Example A — Mifflin–St Jeor
Male, 80 kg, 178 cm, 30 y → BMR = 10·80 + 6.25·178 − 5·30 + 5 = 1,783 kcal.
Light activity: TDEE ≈ 1,783 × 1.375 ≈ 2,453 kcal.

Example B — Katch–McArdle
Female, 65 kg, 30% body fat → LBM = 65 × 0.70 = 45.5 kg.
BMR = 370 + 21.6 × 45.5 ≈ 1,354 kcal.

| Goal | Adjustment | Example (TDEE 2450 kcal) | |---|---|---:| | Weight loss | -10% to -20% | 2,200–2,450 → ~2,200 kcal | | Maintenance | 0% | ~2,450 kcal | | Gain | +5% to +15% | ~2,575–2,820 kcal |

Pro Tips & Best Practices

  • Recalculate after 5–10 lb (2–5 kg) change or training shifts.
  • For athletes, prefer Katch–McArdle if body fat % is known.
  • Match activity level to your real week, not an idealized one.
  • Pair BMR with protein targets and sleep to support recomposition.

Related Calculators

FAQ

Q: What is BMR?

A: Basal Metabolic Rate is the calories your body needs at rest to sustain vital functions.

Q: Which BMR formula is best?

A: Mifflin–St Jeor is widely used for modern populations; Harris–Benedict (revised) and Katch–McArdle (uses body fat %) are alternatives.

Q: How do I get daily calories from BMR?

A: Multiply BMR by an activity factor to get TDEE (Total Daily Energy Expenditure); adjust for weight loss/gain goals.

Q: Does age affect BMR?

A: Yes—BMR typically decreases with age due to changes in lean mass and hormones.

Q: Is BMR the same as RMR?

A: They’re similar; RMR is usually measured less strictly and tends to be slightly higher than BMR.

Compliance note: Informational only; not medical advice.

Call to Action

Estimate your BMR and TDEE, then set a realistic deficit or surplus—adjust weekly based on progress and energy levels.