What Is BMR?
Your Basal Metabolic Rate is the energy your body burns at complete rest — powering your brain, heart, breathing, and cell maintenance. It typically accounts for 60–75 % of all calories you burn in a day, more than exercise for most people.
The Formulas
This calculator shows two estimates. The Mifflin-St Jeor equation (1990) is recommended by the Academy of Nutrition and Dietetics as the most accurate for the general population:
Men: 10×kg + 6.25×cm − 5×age + 5
Women: 10×kg + 6.25×cm − 5×age − 161
The revised Harris-Benedict equation (1984) is shown for comparison; it tends to read slightly higher.
Worked Example
A 30-year-old woman, 165 cm, 60 kg: BMR = 600 + 1,031 − 150 − 161 ≈ 1,320 kcal/day. Even doing nothing, her body needs about that much energy.
What Changes Your BMR
- Muscle mass raises it — muscle burns more at rest than fat, one reason strength training helps long-term weight management.
- Age lowers it gradually, largely through muscle loss.
- Severe dieting can suppress it (adaptive thermogenesis) — another argument for moderate deficits.
Formula estimates are ±10 % for most people. Metabolic testing (indirect calorimetry) gives exact values.