THE NUMORIX GUIDE
How to use the Basal Metabolic Rate Calculator
Last reviewed September 14, 2026
What this calculator does
The route uses Mifflin-St Jeor: BMR = 10 * weightKg + 6.
Formula and method
The route uses Mifflin-St Jeor: BMR = 10 * weightKg + 6.25 * heightCm - 5 * age + 5 for the male equation option, or the same terms minus 161 for the female option. Imperial inputs are converted with 1 in = 2.54 cm and 1 lb = 0.45359237 kg, then the result is rounded to a whole calorie per day.
Variables and inputs
Enter age in years, select metric or imperial units, choose the sex used by the equation, and enter height and weight in the units shown. The engine accepts ages 1-120, heights 1-260 cm, and weights 1-500 kg after conversion.
Worked example
For the default female equation with age 30, height 170 cm, and weight 70 kg: 10 * 70 + 6.25 * 170 - 5 * 30 - 161 = 1451.5, which rounds to 1,452 calories/day.
How to interpret the result
BMR is an estimate of energy use at rest under the equation's assumptions. It is not a daily eating target: activity, digestion, body composition, illness, pregnancy, and goals affect total daily energy needs.
Common mistakes to avoid
Use the unit toggle before entering height and weight, and choose the equation profile intentionally. Do not multiply BMR by an activity factor unless you are building a separate TDEE estimate, and do not treat the rounded value as a measured metabolic rate.
Assumptions and limitations
Mifflin-St Jeor is a population equation with individual error. It does not measure metabolism, model body composition, or adjust for medical conditions, pregnancy, breastfeeding, medications, or unusual activity. The sex selector is an equation parameter, not a full description of physiology.