BMR Calculator (Basal Metabolic Rate)
Calculate your Basal Metabolic Rate using the Harris-Benedict or Mifflin-St Jeor equation.
Find your daily calorie burn at rest.
BMR stands for Basal Metabolic Rate — the calories your body burns just to stay alive while completely at rest. Breathing, heartbeat, body temperature regulation, organ function, brain activity. If you stayed in bed all day and didn’t move, you’d still burn this many calories.
BMR typically accounts for 60-75% of your total daily calorie burn. The rest comes from movement, exercise, and the small amount of energy used to digest food.
Two Formulas (This Calculator Uses Both)
The result shows numbers from both equations so you can compare.
Mifflin-St Jeor (1990) — recommended, more accurate:
- Men: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5
- Women: BMR = (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161
Original Harris-Benedict (1919) — widely used historically:
- Men: BMR = 88.362 + (13.397 × weight kg) + (4.799 × height cm) − (5.677 × age)
- Women: BMR = 447.593 + (9.247 × weight kg) + (3.098 × height cm) − (4.330 × age)
Mifflin-St Jeor is more accurate for modern populations and is what most current sports nutrition references use. Harris-Benedict tends to overestimate by roughly 5%.
BMR Versus TDEE
TDEE stands for Total Daily Energy Expenditure — what you actually burn in a normal day. TDEE = BMR × an activity factor:
| Activity Level | Multiplier |
|---|---|
| Sedentary (desk job, no exercise) | × 1.2 |
| Lightly active (1-3 days/week) | × 1.375 |
| Moderately active (3-5 days/week) | × 1.55 |
| Very active (6-7 days/week) | × 1.725 |
| Extra active (physical job + daily training) | × 1.9 |
This calculator shows your TDEE at every level so you can see the range.
What Affects BMR
- Age — BMR drops about 2% per decade after age 20
- Sex — Men typically have higher BMR due to more muscle and less essential fat
- Lean mass — Muscle burns roughly 6 calories per pound at rest; fat burns about 2. Strength training over years measurably raises your BMR
- Genetics — Real BMR varies 10-15% from formula predictions; some people just run hotter or cooler
- Hormones — Thyroid disorders, testosterone, and cortisol all shift the number
Worked Example
30-year-old woman, 65 kg, 165 cm:
BMR (Mifflin-St Jeor) = (10 × 65) + (6.25 × 165) − (5 × 30) − 161 = 650 + 1,031.25 − 150 − 161 = 1,370 kcal/day
For comparison, Harris-Benedict on the same inputs:
BMR = 447.593 + (9.247 × 65) + (3.098 × 165) − (4.330 × 30) ≈ 1,430 kcal/day — about 60 kcal higher
Most reliable real-world test: track your weight and food intake for two weeks at maintenance. The number that keeps your weight stable is your true TDEE. Divide by your activity multiplier and you have your real BMR.