Basal Metabolic Rate Calculator Online
BMR Calculator
Basal Metabolic Rate Calculator
The BMR calculator finds your Basal Metabolic Rate: the number of calories your body burns at complete rest in 24 hours to keep organs functioning. BMR is the starting point for calculating your total daily calorie needs.
BMR Formulas Compared
Two main formulas are in use. Mifflin-St Jeor (1990) is more accurate for most modern adults and is the preferred formula in most dietitian settings. Harris-Benedict (revised 1984) is older and slightly overpredicts BMR. Both are estimates with a margin of roughly 10%.
| Formula | Men | Women |
|---|---|---|
| Mifflin-St Jeor | (10 x kg) + (6.25 x cm) - (5 x age) + 5 | (10 x kg) + (6.25 x cm) - (5 x age) - 161 |
| Harris-Benedict | 88.362 + (13.397 x kg) + (4.799 x cm) - (5.677 x age) | 447.593 + (9.247 x kg) + (3.098 x cm) - (4.330 x age) |
Sample BMR Values
| Person | Weight | Height | Age | BMR (Mifflin) |
|---|---|---|---|---|
| Woman | 60 kg | 163 cm | 30 | 1,378 kcal |
| Woman | 75 kg | 168 cm | 45 | 1,507 kcal |
| Man | 75 kg | 178 cm | 30 | 1,793 kcal |
| Man | 90 kg | 183 cm | 45 | 1,920 kcal |
BMR vs. TDEE
BMR is the minimum calories you need at rest. TDEE (Total Daily Energy Expenditure) adds physical activity on top of BMR. Multiply BMR by your activity factor (1.2 to 1.9) to estimate TDEE. Eating at BMR for extended periods causes muscle loss and metabolic adaptation. Eating at TDEE with a small deficit is the recommended approach for fat loss.
Factors That Affect BMR
Muscle mass raises BMR because muscle tissue burns more calories at rest than fat tissue. Age lowers BMR by roughly 1-2% per decade after 30 due to muscle loss. Hormonal conditions (hypothyroidism, PCOS) can lower BMR significantly. Body temperature, climate, and prolonged severe calorie restriction also affect BMR.
Frequently Asked Questions
What is BMR and how is it different from TDEE?⌄
BMR (Basal Metabolic Rate) is the calories you burn doing absolutely nothing, at complete rest. TDEE (Total Daily Energy Expenditure) is BMR multiplied by an activity factor that accounts for movement and exercise. Eat at or near TDEE for maintenance; eat below TDEE for fat loss.
How do I calculate my BMR?⌄
Use the Mifflin-St Jeor formula: for women, (10 x weight in kg) + (6.25 x height in cm) - (5 x age) - 161. For men, replace the -161 with +5. Or enter your stats in this calculator and get the result instantly.
Does BMR change with age?⌄
Yes. BMR decreases by about 1-2% per decade after age 30, primarily because muscle mass naturally declines with age. Strength training slows this decline by preserving muscle tissue, which keeps BMR higher than it would be otherwise.
Should I eat my BMR to lose weight?⌄
No. Eating only at BMR creates too large a deficit for most people and risks nutrient deficiency, muscle loss, and metabolic slowdown. A deficit of 300-500 calories below TDEE (not BMR) is the recommended approach for sustainable fat loss.
How does muscle mass affect BMR?⌄
Muscle tissue burns roughly 6-10 kcal per pound per day at rest. Fat tissue burns about 2 kcal per pound per day. People with more muscle mass have meaningfully higher BMRs. This is why resistance training supports long-term weight management even on rest days.