BMR Calculator Using the Mifflin–St Jeor Equation

This calculator estimates the energy your body uses in a day at rest. It uses the Mifflin–St Jeor equations and reports the result in kilocalories per day (kcal/day).

Online tools often call this result basal metabolic rate (BMR). More precisely, the Mifflin–St Jeor study developed an equation for resting energy expenditure (REE). A laboratory measurement and a formula-based estimate are not interchangeable.

Inputs and method

Enter:

• sex used by the published equation;
• age in years;
• height in centimetres;
• weight in kilograms.

The calculator applies:

• Male equation: 10 × weight + 6.25 × height − 5 × age + 5
• Female equation: 10 × weight + 6.25 × height − 5 × age − 161

Weight is in kilograms and height is in centimetres. The constant is the only difference between the two versions implemented by this tool.

Worked example

For a 30-year-old male who is 170 cm tall and weighs 70 kg:

10 × 70 + 6.25 × 170 − 5 × 30 + 5

= 700 + 1,062.5 − 150 + 5

= 1,617.5 kcal/day

SoupCalc therefore displays 1,617.50 kcal/day. The same inputs with the female equation produce 1,451.50 kcal/day.

What the result means

The result is a resting-energy estimate, not a recommended food intake. Total daily energy expenditure also includes movement, planned exercise, digestion, growth, recovery, and other physiological demands. Multiplying the estimate by an activity factor introduces another layer of uncertainty.

Do not interpret a difference of a few calories as meaningful precision. The calculator shows two decimal places so the calculation can be reproduced, not because an individual's metabolism can be predicted that precisely.

Accuracy and limitations

The original Mifflin–St Jeor equation was derived from 498 adults aged 19–78. Prediction error for an individual can be material. A systematic review found it was among the more reliable commonly used equations, but even the better equations did not predict every person's measured resting metabolic rate closely.

Results may be less representative during pregnancy, growth, acute illness, recovery from injury, substantial muscle loss, very high athletic training, or when body composition differs greatly from the populations used to derive the equation. Medicines and endocrine conditions can also affect energy expenditure.

Indirect calorimetry performed under controlled conditions is used when a measured value is clinically important. Discuss nutrition targets with a qualified clinician or dietitian when the result will be used for treatment, a medically supervised diet, an eating disorder, or another health condition.

Sources

• Mifflin et al. (1990) — A new predictive equation for resting energy expenditure in healthy individuals
• Frankenfield et al. (2005) — Comparison of predictive equations for resting metabolic rate: a systematic review

Editorial record

Written and manually reviewed by the SoupCalc Editorial Team. Formula and examples were checked against the current calculator implementation. Last reviewed: August 10, 2026. No external medical reviewer participated. This page remains unavailable for indexing and advertising until every approved locale passes review.