BMR Calculator
Calculate Basal Metabolic Rate using Mifflin-St Jeor equation.
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How This BMR Calculator Works
This calculator uses established scientific formulas validated in peer-reviewed literature. All calculations run locally in your browser — no data is sent to any server.
BMR by Age and Gender (Average)
| Age | Men (cal/day) | Women (cal/day) |
|---|---|---|
| 18–25 | 1,800 – 2,000 | 1,400 – 1,600 |
| 26–35 | 1,700 – 1,900 | 1,350 – 1,550 |
| 36–45 | 1,600 – 1,800 | 1,300 – 1,500 |
| 46–55 | 1,500 – 1,700 | 1,250 – 1,450 |
| 56–65 | 1,400 – 1,600 | 1,200 – 1,400 |
| 66+ | 1,300 – 1,500 | 1,100 – 1,300 |
What Affects Your BMR
Lean muscle mass is the biggest factor you can control. Each pound of muscle burns ~6–7 calories per day at rest vs ~2–3 for fat. Build muscle through resistance training — track with the One Rep Max Calculator. Age reduces BMR ~1–2% per decade from sarcopenia (muscle loss). Gender: men typically have higher BMR due to greater lean mass. Genetics account for 6–10% individual variation.
BMR vs TDEE vs Calorie Needs
BMR is your floor — calories burned doing nothing. Multiply by activity factor to get TDEE. Then adjust for goals using the Calorie Calculator. Split into macros with the Macro Calculator. The chart above shows your estimated TDEE at each activity level — pick the one matching your lifestyle.
The Mifflin-St Jeor Equation Explained
This calculator uses the Mifflin-St Jeor equation (1990), which the American Dietetic Association identified in a 2005 evidence review as the most accurate predictive equation for estimating resting energy expenditure in healthy individuals. It replaced the older Harris-Benedict equation (1919), which overestimates BMR by approximately 5% in modern populations.
The equation accounts for four variables: weight contributes 10 calories per kilogram, height adds 6.25 calories per centimeter, age subtracts 5 calories per year (reflecting the metabolic decline of aging), and a gender constant of +5 for men or -161 for women reflects differences in lean mass and hormonal profile.
How to Increase Your BMR
Build lean muscle mass: This is the most effective strategy. Each pound of muscle burns approximately 6-7 calories per day at rest, compared to 2-3 for fat. Progressive resistance training using loads based on your one-rep max is the most evidence-based approach to building muscle. Combine with adequate protein intake (1.6-2.2g/kg) to support muscle protein synthesis.
Avoid extreme calorie restriction: Severe diets (below 1,200 calories) trigger metabolic adaptation, where your body reduces BMR to conserve energy. Instead, use a moderate 500-calorie deficit below your TDEE calculated with the Calorie Calculator.
Stay active throughout the day: Non-Exercise Activity Thermogenesis (NEAT) — fidgeting, standing, walking — can vary by 500-1,000 calories per day between individuals. Track your formal exercise with the Calories Burned Calculator, but don't underestimate daily movement.
Prioritize sleep: Sleep deprivation reduces BMR by 2-5% and increases hunger hormones. Use our Sleep Calculator to optimize your sleep cycles. Research shows 7-9 hours of quality sleep is essential for metabolic health.
Stay hydrated: Studies show that drinking 500ml of water can temporarily boost metabolic rate by 24-30% for about an hour. Check your needs with the Water Intake Calculator.
Frequently Asked Questions
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