BMR Calculator
Basal Metabolic Rate, TDEE, and daily calorie targets — 3 clinical formulas compared
BMR (Basal Metabolic Rate) is the number of calories your body burns at complete rest just to stay alive. This calculator computes your BMR three ways — Mifflin-St Jeor, Revised Harris-Benedict, and Katch-McArdle (if you know your body fat %) — then converts it to your TDEE (Total Daily Energy Expenditure) and exact daily calorie targets for weight loss, maintenance, or muscle gain.
How BMR and TDEE Are Calculated
BMR represents 60–75% of the calories you burn each day, before accounting for movement. This calculator runs all three widely-used clinical formulas side by side so you can see how they compare, then applies your activity level to get TDEE — the number that actually drives weight loss, maintenance, or gain targets.
| Variable | Definition |
|---|---|
| BMR | Basal Metabolic Rate — calories burned completely at rest |
| TDEE | Total Daily Energy Expenditure — BMR × activity multiplier |
| W, H, A | Weight (kg), Height (cm), Age (years) |
| Lean Body Mass | Total weight minus fat mass (weight × (1 − body fat %)) |
Worked example: Male, age 35, 5'10" (177.8 cm), 185 lbs (83.9 kg). Mifflin-St Jeor: BMR = (10×83.9) + (6.25×177.8) − (5×35) + 5 = 839 + 1,111 − 175 + 5 = 1,780 cal/day. Revised Harris-Benedict: BMR = (13.397×83.9) + (4.799×177.8) − (5.677×35) + 88.362 ≈ 1,825 cal/day. At moderate activity (1.55×), TDEE using Mifflin-St Jeor = 1,780 × 1.55 = 2,759 cal/day to maintain weight. To lose 1 lb/week: eat 2,259 cal/day.
🔥 Metabolism Expert Insight
Your BMR Isn't Fixed — And Crash Diets Make It Worse: Prolonged, severe calorie restriction triggers "adaptive thermogenesis" — your body actually lowers its BMR beyond what weight loss alone would predict, as a survival mechanism. This is a major reason crash diets backfire long-term. The fix: never cut more than 20–25% below your TDEE, prioritize protein (0.7–1g per lb of body weight) to preserve muscle (which drives BMR), and take periodic diet breaks at maintenance calories every 8–12 weeks if cutting for an extended period. Strength training is the single best lever for raising your BMR over time, since muscle tissue burns more at rest than fat tissue.
BMR Calculator FAQ
What is BMR (Basal Metabolic Rate)?
BMR is the number of calories your body burns in 24 hours while doing absolutely nothing — just keeping your heart beating, lungs breathing, and organs functioning. It typically accounts for 60–75% of total daily calorie burn.
Which BMR formula is most accurate?
Mifflin-St Jeor is considered the most accurate for the general population and is what most dietitians use today. Katch-McArdle is more accurate for lean or athletic individuals since it's based on lean body mass — but requires an accurate body fat % estimate.
What is the difference between BMR and TDEE?
BMR is calories burned at complete rest. TDEE is BMR multiplied by an activity factor (1.2–1.9) to account for movement and exercise. TDEE is the number that actually drives your calorie target for losing, maintaining, or gaining weight.
Does eating below my BMR slow my metabolism?
Eating below TDEE is required for weight loss, but eating far below BMR for extended periods can trigger metabolic adaptation and muscle loss. Stay above 1,200 cal/day (women) or 1,500 cal/day (men) without medical supervision.
Why do the three formulas give different results?
Each formula was derived from a different research population. A ±5–10% spread between formulas is normal — use the average as your starting estimate, then adjust based on 2–3 weeks of real-world tracking against actual weight change.
BMR Calculator — Basal Metabolic Rate & TDEE
Your Stats
Your Results
Based on your results — what to do next:
Turn your BMR into a full calorie plan
Your BMR of 1,780 cal/day burns 2,759 cal/day at your activity level. See macro-adjusted meal targets in the Calorie Calculator.
Check your BMI and healthy weight range
See how your 185 lb weight compares to your healthy range for your height.
Split your calories into macros
At 2,759 cal/day, get exact protein, carb, and fat gram targets for cutting, bulking, or maintaining.
Next Step: Related Calculators
Calorie Calculator (TDEE)
Daily calorie needs for weight loss, maintenance, or muscle gain using Mifflin-St Jeor.
Ideal Weight Calculator
Ideal body weight from all four clinical formulas (Devine, Robinson, Miller, Hamwi) plus your healthy BMI range.
Pace Calculator
Running pace, finish time, or distance — with splits, track lap times, and predicted race results.