BMR Calculator (Basal Metabolic Rate)

What BMR measures

Basal metabolic rate is the energy your body uses at complete rest to keep you alive: breathing, circulation, temperature control and cell repair. For most people it is the largest part of daily energy use, typically 60 to 70 percent. This calculator uses the Mifflin-St Jeor equation, which studies have found to be the most accurate of the common prediction equations for healthy adults.

For men the equation is 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5. For women the final constant is −161 instead of +5. Each term reflects a real effect: more body mass burns more energy, taller people have more tissue, and metabolism slows slightly with age.

Worked example

A 30-year-old woman who weighs 60 kg and is 165 cm tall: 10 × 60 = 600, 6.25 × 165 = 1,031.25, and 5 × 30 = 150. Adding and subtracting gives 600 + 1,031.25 − 150 − 161 = 1,320 kcal per day. That is what she would burn lying still all day; her total daily energy expenditure is higher once activity is included.

Using BMR sensibly

BMR is an estimate with an error of roughly ±10 percent for most people, because body composition, genetics and thyroid function vary. Do not eat below your BMR for long periods without medical advice. To plan intake, multiply BMR by an activity factor (the TDEE calculator does this) and adjust slowly based on how your weight actually changes over several weeks.