Calories your body burns at complete rest. Uses the Mifflin–St Jeor equation.
What does BMR mean?
Basal Metabolic Rate (BMR) represents the minimum amount of energy your body needs to sustain essential physiological functions, breathing, maintaining body temperature, circulation, cell production, and organ function, while in a state of complete physical and digestive rest. It is measured after at least 8 hours of sleep in a post-absorptive state (no food for 12 hours).
This calculator uses the Mifflin–St Jeor equation, published in the American Journal of Clinical Nutrition in 1990. A large validation study comparing six BMR equations found it to be the most accurate for most adults, overestimating true BMR by about 5% on average versus 14% for the older Harris-Benedict equation.
The Mifflin formula is: for men, (10 × weight kg) + (6.25 × height cm) − (5 × age) + 5; for women, (10 × weight kg) + (6.25 × height cm) − (5 × age) − 161. The BMR you get here is your floor, the absolute minimum calorie intake to keep your organs functioning. Multiply by an activity factor to get your Total Daily Energy Expenditure (TDEE).
Several factors raise or lower BMR: muscle mass (more muscle = higher BMR), thyroid hormone levels, body temperature, certain medications, pregnancy, and chronic illness. Athletes typically have a BMR 5–10% higher than sedentary individuals of the same size.
Reference ranges
| Category | BMR (kcal/day) | Context |
|---|---|---|
| Low (small / older female) | 1,100 – 1,400 | Normal for shorter, lighter, older women |
| Typical female | 1,400 – 1,700 | Average adult woman |
| Typical male | 1,700 – 2,100 | Average adult man |
| High (large / muscular male) | 2,100 – 2,600+ | Tall, heavy, or highly muscular men |
When should you see a doctor?
A BMR calculation is not a clinical test and requires no medical supervision. However, if you suspect an unusually high or low metabolic rate, for example you gain weight eating very little, or lose weight despite eating normally, it is worth discussing thyroid function, adrenal health, or other metabolic conditions with a doctor, as no self-calculated BMR tool can diagnose these conditions.