Metabolism Calculator

Your body's baseline

Calculate your Basal Metabolic Rate (BMR) — the calories your body burns just to stay alive — and your Total Daily Energy Expenditure (TDEE).

Mifflin-St Jeor BMR More accurate for most people
Harris-Benedict BMR Revised 1984 equation
Total Daily Energy Expenditure (TDEE)

Daily calorie targets by goal

Lose fat
−20% deficit
Maintain
TDEE
Build muscle
+10% surplus

BMR is calories burned at complete rest. TDEE includes your activity level. Use TDEE as the starting point for any diet plan.

What is BMR?

Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain basic life functions — breathing, circulation, cell production, and temperature regulation. It accounts for 60–75% of your total daily calorie expenditure.

BMR varies primarily by body size, age, sex, and body composition. Muscle tissue burns more calories at rest than fat tissue, which is why muscular individuals tend to have higher BMRs.

Mifflin-St Jeor vs. Harris-Benedict

This BMR calculator provides results from both major formulas. Mifflin-St Jeor (1990) is considered more accurate for modern populations and is recommended by the American Dietetic Association. Harris-Benedict (revised 1984) is the older standard and tends to give slightly higher estimates.

For most people, the Mifflin-St Jeor result is the better starting point. If you find that number leads to unexpected weight changes, adjust by 100–200 calories.

BMR vs. TDEE

BMR is your resting calorie burn. TDEE (Total Daily Energy Expenditure) is your BMR multiplied by an activity factor — it represents the total calories you actually burn in a day, including exercise, walking, and daily movement.

TDEE is the number that matters for diet planning: eat below it to lose weight, at it to maintain, or above it to gain. The calorie targets shown above use your TDEE as the baseline.

Frequently asked questions

Can I increase my BMR?

Yes. Building muscle mass is the most effective way to raise your BMR, since muscle tissue burns more calories at rest than fat. Resistance training, adequate protein intake, and avoiding crash diets (which lower BMR) all help.

Why does BMR decrease with age?

Primarily due to loss of muscle mass (sarcopenia), hormonal changes, and reduced physical activity. This is why maintaining strength training becomes increasingly important as you age.

Should I eat below my BMR to lose weight?

Generally, no. Eating below your BMR for extended periods can trigger metabolic adaptation, muscle loss, and nutrient deficiencies. A safer approach is eating 15–20% below your TDEE while keeping calories above your BMR.

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