How BMR Is Calculated
Your basal metabolic rate is the energy your body burns at complete rest — powering your heart, lungs, brain and cell repair. It's typically 60–70% of everything you burn in a day.
This tool leads with the Mifflin-St Jeor equation, the modern clinical standard: BMR = 10×weight(kg) + 6.25×height(cm) − 5×age + 5 (men) or − 161 (women). Example: a 30-year-old man at 75 kg / 175 cm burns 10×75 + 6.25×175 − 5×30 + 5 ≈ 1,699 kcal/day at rest. The older Harris-Benedict figure is shown alongside for comparison.
To estimate what you actually burn in a day (TDEE), your BMR is multiplied by an activity factor from 1.2 (desk job, little exercise) to 1.9 (athlete / physical job) — the full table updates live above. Eating below your TDEE loses weight; above it gains.
Want goal-based targets? The Calorie Calculator turns these numbers into loss/maintain/gain plans, the BMI Calculator checks your weight range, and the Sleep Calculator covers the recovery side.