BMR Calculator

Estimate your Basal Metabolic Rate (BMR) — the calories your body burns at rest — using the Mifflin–St Jeor Equation. Supports both imperial and metric units.

Written & reviewed by the FinanceMaxing Editorial Team · Updated July 21, 2026 · How we calculate

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About the BMR Calculator

The BMR Calculator estimates your Basal Metabolic Rate — the number of calories your body needs each day to sustain essential life functions at complete rest. BMR accounts for roughly 60–75% of your total daily calorie burn, making it the most important factor in any calorie or weight management plan.

Mifflin–St Jeor Formula (Used Here)

Men:   BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161

This formula, published in 1990, is widely regarded as the most accurate for estimating BMR in diverse modern populations. It is preferred over the older Harris-Benedict equation, which tends to overestimate calorie needs.

Example Calculation

Male, age 30, 5'10" (177.8 cm), 175 lb (79.4 kg):
BMR = (10 × 79.4) + (6.25 × 177.8) − (5 × 30) + 5
BMR = 794 + 1,111 − 150 + 5 = 1,760 calories/day

From BMR to TDEE

BMR only tells you what you burn at rest. TDEE (Total Daily Energy Expenditure) estimates total daily calorie burn by applying an activity factor:

  • Sedentary (desk job, little exercise): BMR × 1.2
  • Lightly active (1–3 days/week exercise): BMR × 1.375
  • Moderately active (3–5 days/week): BMR × 1.55
  • Very active (6–7 days/week hard exercise): BMR × 1.725
  • Extra active (physical job + daily training): BMR × 1.9

Use the Calorie Calculator to compute your full TDEE with activity level.

What Affects Your BMR?

  • Muscle mass — the single biggest controllable factor; muscle burns ~3× more calories than fat at rest. Track your muscle-to-fat ratio with the Body Fat Calculator.
  • Age — BMR declines roughly 1–2% per decade after age 20 due to muscle loss
  • Sex — men typically have 5–10% higher BMR than women of the same height/weight due to greater lean mass
  • Body size — larger people have more tissue to maintain and thus higher BMR
  • Thyroid function — hypothyroidism lowers BMR; hyperthyroidism raises it significantly
  • Very low-calorie dieting — prolonged severe restriction triggers metabolic adaptation, lowering BMR

Using BMR for Weight Goals

  • Lose fat: Eat 10–20% below TDEE. A 500 cal/day deficit ≈ 0.5 kg (1 lb) per week loss.
  • Build muscle: Eat 5–15% above TDEE with adequate protein (1.6–2.2 g/kg body weight)
  • Maintain weight: Match your TDEE as closely as possible

These are estimates — individual variation is real. Track actual weight changes over 2–4 weeks and adjust as needed. Use the BMI Calculator for a quick weight-status check alongside your BMR.

Frequently Asked Questions

What is BMR?

BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest — just to keep you alive. It accounts for involuntary functions like breathing, circulation, cell production, temperature regulation, and organ function. BMR represents approximately 60–75% of the average person's total daily calorie burn.

How is BMR calculated?

This calculator uses the Mifflin–St Jeor Equation, which is widely considered the most accurate BMR formula for most people. Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5. Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161.

What is the difference between Mifflin–St Jeor and Harris-Benedict?

Both are BMR formulas, but Mifflin–St Jeor (1990) is considered more accurate for modern populations. Harris-Benedict (1919, revised 1984) tends to overestimate calorie needs by about 5%. Most dietitians now prefer Mifflin–St Jeor. This calculator uses Mifflin–St Jeor.

What is a typical BMR for men and women?

Averages vary by size, age, and muscle mass, but a typical range: Men — 1,600 to 2,200 calories/day. Women — 1,300 to 1,800 calories/day. Younger people, heavier individuals, and those with more muscle mass have higher BMRs. BMR declines roughly 1–2% per decade after age 20.

Does BMR include exercise?

No. BMR is your resting calorie burn only — it assumes you are completely still for 24 hours. To estimate actual daily calorie needs, multiply BMR by an activity factor to get TDEE (Total Daily Energy Expenditure). See the Calorie Calculator for a full TDEE estimate.

What factors increase or decrease BMR?

BMR is higher with: more muscle mass (muscle burns more calories than fat), larger body size, younger age, male sex, fever, and pregnancy. BMR is lower with: aging, very low-calorie dieting (metabolic adaptation), loss of muscle mass, and hypothyroidism.

How do I use BMR for weight loss or gain?

First calculate TDEE (BMR × activity factor). Then: to lose weight, aim for a daily intake 10–20% below TDEE; to gain muscle, aim 5–15% above TDEE; to maintain, match TDEE. A 500 calorie/day deficit below TDEE typically produces approximately 0.5 kg (1 lb) of weight loss per week.

Can I use BMR to plan a diet?

Yes — BMR is the starting point. After finding your TDEE, you can set a calorie target and distribute macronutrients (protein, carbs, fat). A common starting point for fat loss: 1g protein per lb body weight, with remaining calories split between carbs and fat. Always consult a registered dietitian for personalized guidance.