BMR Calculator

What this calculator does

This calculator estimates your Basal Metabolic Rate (BMR)—the number of calories your body burns at rest to maintain vital functions (breathing, circulation, cell production, etc.). It also shows your Total Daily Energy Expenditure (TDEE) when you choose an activity level. BMR and TDEE are in calories per day.

BMR does not include activity; TDEE = BMR × activity multiplier, and is used to set maintenance calories for diet planning. Typical users include people planning weight loss or gain, athletes setting calorie targets, and anyone curious about their resting metabolism. It is an estimate only; individual variation is large.

How to use it

1. Choose Unit: Metric (kg, cm) or Imperial (lb, ft/in).
2. Enter weight and height (and for imperial, height in ft and in).
3. Enter Age (years) and Sex (Male/Female).
4. Select Activity level (Sedentary to Very active) to get TDEE.
5. Choose BMR formula: Mifflin-St Jeor (default), Harris-Benedict, or Katch-McArdle.
6. If you select Katch-McArdle, enter Body fat % (required for that formula).
7. Read BMR and TDEE in the Result panel.

All inputs are in the "Inputs" section; the result updates as you change values.

Formulas used

Mifflin-St Jeor (1990)

Often recommended as the default for most adults. Derived from a more recent dataset than Harris-Benedict.

• Male: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5
• Female: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161

Result in kcal/day. Use when you do not have a body fat estimate.

Harris–Benedict (revised, 1984)

Widely used historically; tends to run slightly higher than Mifflin-St Jeor.

• Male: BMR = 13.397 × weight(kg) + 4.799 × height(cm) − 5.677 × age + 88.362
• Female: BMR = 9.247 × weight(kg) + 3.098 × height(cm) − 4.330 × age + 447.593

Use for comparison or when following older guidelines.

Katch–McArdle

Uses lean body mass instead of total weight, so it can be more accurate if you know your body fat %.

• BMR = 370 + 21.6 × lean mass(kg)
• Lean mass = weight(kg) × (1 − body fat % / 100)

Requires a body fat estimate (e.g. from a body fat calculator or calipers). Best when body composition is known.

Interpretation & examples

• BMR is only the "at rest" component. Typical adult BMR ranges are roughly 1,200–2,000+ kcal/day depending on size, age, and sex.
• TDEE is what you use for "maintenance" calories. For weight loss, eat below TDEE; for gain, above it.
• Example 1: 70 kg, 170 cm, 30 years, male, moderate activity → BMR ≈ 1,650 kcal/day, TDEE ≈ 2,560 kcal/day (formula-dependent).
• Example 2: 60 kg, 165 cm, 25 years, female, light activity → BMR ≈ 1,350 kcal/day, TDEE ≈ 1,856 kcal/day.
• Example 3: Same person with Katch-McArdle and 22% body fat → BMR based on lean mass; often slightly lower than Mifflin-St Jeor for the same stats.

History & background

Harris–Benedict (1919, revised 1984) was the standard for decades and is still cited in many textbooks. Mifflin–St Jeor (1990) was derived from a more recent dataset and is often preferred in current guidelines (e.g. Academy of Nutrition and Dietetics). Katch–McArdle is used when body composition (lean mass) is known and is common in fitness and bodybuilding. All three are population equations; individual metabolism varies with genetics, health, and medication.

Limitations & safety notes

• These are estimates, not medical advice. Individual variation is large (metabolism, health, medication, etc.).
• Do not use BMR/TDEE as the sole basis for severe restriction. Very low intake can be harmful; many guidelines suggest a minimum of about 1,200 kcal/day for women and 1,500 for men unless under supervision.
• For medical conditions, pregnancy, eating disorders, or personalized nutrition, consult a doctor or dietitian. This tool is for education and rough planning only.