Calculate your Basal Metabolic Rate (BMR) — the energy your body needs at rest to maintain vital functions.
BMR is the minimum number of calories your body needs to function while at rest. It accounts for about 60-75% of your total daily energy expenditure.
A BMR calculator answers the single most important question for anyone serious about weight management: “If I did absolutely nothing all day — just lay in bed and breathed — how many calories would my body burn to keep me alive?”
Basal Metabolic Rate (BMR) is the number of calories your body needs at complete rest to keep your heart pumping, your lungs expanding, your brain functioning, and your cells regenerating. It accounts for a staggering 60–75% of the calories you burn each day — far more than exercise or digestion. Your BMR is essentially your body's idling speed.
Unlike a calorie calculator (which factors in your daily activity), a BMR calculator strips everything away. It tells you the minimum calories your body requires just to exist. Once you know your BMR, you multiply it by an activity factor to get your Total Daily Energy Expenditure (TDEE).
The 2026 Reality: With metabolic health awareness at an all‑time high, more people are using BMR calculators to guide their nutrition. The Mifflin‑St Jeor equation (developed in 1990) has largely replaced the older Harris‑Benedict formula (from 1919) because it's more accurate for modern populations.
Men: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) + 5
Women: BMR = (10 × weight in kg) + (6.25 × height in cm) – (5 × age in years) – 161
Man Example (35y, 81.6kg, 177.8cm):
816 + 1,111 – 175 + 5 = 1,757 calories/day
Pro Tip: Weigh yourself in the morning after using the bathroom, before eating or drinking. Use barefoot height for accuracy.
Developed in 1919 and revised in 1984. While still used, it tends to slightly overestimate calorie needs in modern populations by about 5%.
Men: 66.47 + (13.75 × kg) + (5.003 × cm) – (6.755 × age)
Women: 655.1 + (9.563 × kg) + (1.85 × cm) – (4.676 × age)
If you know your body fat %, this is significantly more accurate because it uses lean body mass — the metabolically active tissue.
BMR = 370 + (21.6 × Lean Body Mass in kg)
LBM = Total weight × (1 – Body Fat %)
| Activity Level | Description | Multiplier |
|---|---|---|
| Sedentary | Little or no exercise, desk job | 1.2 |
| Lightly active | Light exercise 1‑3 days/week | 1.375 |
| Moderately active | Moderate exercise 3‑5 days/week | 1.55 |
| Very active | Hard exercise 6‑7 days/week | 1.725 |
| Extra active | Physical job + hard exercise daily | 1.9 |
Weight Loss: TDEE – 300 to 500 (0.5‑1 lb/week)
Maintenance: Eat your TDEE calories
Weight Gain: TDEE + 250 to 500 (Muscle gain)
Important: Never eat below your BMR for extended periods. This can trigger metabolic adaptation and stall progress.
Weight Loss: A smaller body requires fewer calories.
Muscle Gain: Muscle is more metabolically active than fat.
Aging: Decreases about 1‑2% per decade after 30.
Crash Dieting: Lowers BMR to conserve energy.
Using BMR as maintenance: BMR is for a coma. TDEE is what you actually need.
Not recalculating: Needs change as you shrink or grow. Recalculate every 10-15 lbs.
Ignoring muscle: If muscular, total-weight formulas will underestimate your needs.
Overestimating activity: Be honest about your daily movement to avoid overeating.
"Bottom Line: BMR is your baseline. Learn the numbers, and you can change the outcome of your fitness journey."
* This calculator is for informational purposes only. Consult a healthcare professional for medical advice.
Explore more tools in the Fitness category