Enter your age, sex, height, weight, and optional body fat percentage to calculate your Basal Metabolic Rate (BMR) — the minimum energy your body burns at rest.
How to use this calculator
Select your unit system (metric or imperial), biological sex, age, height, and weight.
Optionally enter your body fat percentage if known.
Compare your resting energy expenditure across Mifflin-St Jeor, Harris-Benedict, and Katch-McArdle equations.
Use your BMR baseline to establish daily calorie minimums or calculate TDEE.
W = weight in kg, H = height in cm, A = age in years, LBM = Lean Body Mass in kg = W × (1 − BodyFat%).
Example
Male 30y, 175cm, 70kg, 18% body fat → Mifflin: 1,649 kcal/day, Harris-Benedict: 1,695 kcal/day, Katch-McArdle: 1,610 kcal/day.
Key insights
BMR accounts for approximately 60–75% of a sedentary person's total daily energy expenditure.
Mifflin-St Jeor is the primary clinical benchmark because it provides the highest statistical accuracy for modern populations.
Muscle tissue is more metabolically active than fat tissue, burning ~13 kcal/kg/day at rest compared to ~4.5 kcal/kg/day for fat.
BMR naturally declines by 1–2% per decade after age 30, primarily due to age-related loss of lean muscle mass (sarcopenia).
Prolonged severe calorie restriction (crash dieting) can lower BMR through adaptive thermogenesis (metabolic adaptation).
How to interpret your result
Mifflin-St Jeor vs. Harris-Benedict
Mifflin-St Jeor is recommended for general population use. Harris-Benedict tends to overestimate BMR by 5–15% in modern sedentary individuals.
Katch-McArdle (Lean Body Mass)
Katch-McArdle ignores sex and total weight, focusing exclusively on lean mass. It is the most accurate formula for muscular athletes with known body fat %.
BMR as a Hard Calorie Floor
Consuming below your BMR for extended periods is generally discouraged as it can trigger severe fatigue, hormone disruption, and muscle loss.
Frequently asked questions
What is the difference between BMR and RMR?
BMR (Basal Metabolic Rate) is measured in a strictly controlled fasting laboratory state upon waking. RMR (Resting Metabolic Rate) is measured under less rigid resting conditions and is typically 5–10% higher than BMR.
Can I eat below my BMR to lose weight faster?
Eating below your BMR is not recommended because BMR represents the bare minimum energy your vital organs need to function safely.
How can I increase my BMR?
Building lean muscle mass through resistance training is the most effective long-term way to raise your resting metabolic rate.
Related calculators
TDEE Calculator — Calculate your Total Daily Energy Expenditure (TDEE) and BMR to find your daily maintenance calories.
Calorie Calculator — Estimate your daily calorie needs (BMR & TDEE) for maintenance, loss or gain.
Body Fat Calculator — Estimate your body fat percentage, fat mass, and lean mass using the US Navy method.