Metabolism & Nutrition

BMR
Calculator

Calculate your Basal Metabolic Rate and Total Daily Energy Expenditure (TDEE) using 3 validated formulas. Get calorie goals and macro breakdown.

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BMR (kcal)

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TDEE (kcal)

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Weight Loss

Your Body Details

Age

yrs

Height

Weight

BMR Formula

Body Fat % (required for Katch-McArdle)

Basal Metabolic Rate

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kcal / day

Enter details to calculate

Mifflin

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Harris

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BMR

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TDEE

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Weight Loss

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Muscle Gain

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⚡ TDEE by Activity Level

🎯 Calorie Goals

🥩🍚🥑 Macronutrient Breakdown (Maintenance)

Protein 30%

Carbs 45%

Fat 25%

🔬 BMR vs TDEE

📊 TDEE Across Activity Levels

What is BMR and Why Does It Matter?

Your Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to maintain vital functions — breathing, circulation, temperature regulation, and cell repair. BMR accounts for 60–75% of your total daily energy expenditure and is the foundation of all calorie-based nutrition planning.

The Three BMR Formulas

Mifflin-St Jeor (1990) — Most Accurate for Most People: Male: 10W + 6.25H − 5A + 5 Female: 10W + 6.25H − 5A − 161 Harris-Benedict (Revised 1984): Male: 13.397W + 4.799H − 5.677A + 88.362 Female: 9.247W + 3.098H − 4.330A + 447.593 Katch-McArdle (uses Lean Body Mass): BMR = 370 + 21.6 × LBM LBM = Weight × (1 − Body Fat%) W = weight in kg, H = height in cm, A = age in years

Understanding TDEE Activity Multipliers

Total Daily Energy Expenditure (TDEE) = BMR × Activity Factor. The multipliers range from 1.2 (sedentary) to 1.9 (twice-a-day training). Most people overestimate their activity level — choose the lowest level that honestly describes your week.

Nutrition & Metabolism Tips

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Caloric Deficit

A 500 kcal/day deficit from TDEE produces ~0.5kg/week fat loss. Never go below your BMR for extended periods without medical supervision.

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Preserve Muscle

Eating adequate protein (1.6–2.2g/kg LBM) during a deficit preserves lean mass. Combine with resistance training for best body composition.

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Metabolic Adaptation

BMR decreases during prolonged caloric restriction. Diet breaks every 8–12 weeks help reset hormones and prevent metabolic adaptation.

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Track Consistently

Weigh yourself daily at the same time, then use the weekly average. This smooths out water weight fluctuations and gives meaningful trends.

Frequently Asked Questions

How accurate are BMR calculators?

BMR formulas estimate your calorie needs with a margin of error of about ±10–15%. Individual variation in metabolic rate is influenced by genetics, hormones (thyroid), body composition (more muscle = higher BMR), and gut microbiome. The Mifflin-St Jeor formula is accurate within 10% for about 80% of people. For precision, a registered dietitian can arrange indirect calorimetry (the gold standard).

What happens if I eat at or below my BMR?

Consistently eating at or below BMR can lead to muscle loss, hormonal disruption (especially reproductive hormones), nutrient deficiencies, fatigue, and metabolic adaptation (the body reduces BMR further in response). Very low calorie diets (VLCDs) below BMR should only be done under medical supervision, typically for short periods, and always with high protein intake and resistance training.

Does muscle really raise my BMR?

Yes, but the effect is modest — approximately 13 extra kcal per day per kg of muscle gained. So 5kg of new muscle (a significant achievement) raises BMR by about 65 kcal/day. However, muscle tissue also contributes to higher TDEE through increased exercise capacity and non-exercise activity thermogenesis (NEAT), making the total impact larger than the resting number suggests.

Should I use the Katch-McArdle formula?

The Katch-McArdle formula is more accurate for lean and muscular individuals because it uses Lean Body Mass rather than total weight. If you have an accurate body fat measurement (from DEXA, hydrostatic weighing, or BodPod), Katch-McArdle will give better results than Mifflin. For most people without precise body fat data, Mifflin-St Jeor is the recommended choice.

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Calorie Calculator

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Ideal Weight Calculator

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Lean Body Mass Calculator

LBM for Katch-McArdle formula