BMR and daily calorie calculator (Mifflin–St Jeor)

This calculator is for education. It isn’t medical or dietary advice.

The formula

$$\text{BMR} = 10W + 6.25H - 5A + s$$

$W$ is weight in kg, $H$ height in cm, $A$ age in years, and $s$ is $+5$ for men or $-161$ for women. The result is in kilocalories (the “calories” on food labels) per day.

$$\text{daily calories} = \text{BMR} \times \text{activity factor}$$

Where it comes from

Basal metabolic rate is the energy your body burns at complete rest, just keeping organs running. It’s measured by indirect calorimetry: the oxygen you breathe in and carbon dioxide you breathe out show how much fuel you’re burning.

In 1990, Mark Mifflin, Sachiko St Jeor and colleagues measured the resting energy use of 498 healthy adults aged 19 to 78, about half of them obese. They then fitted a linear regression to find which body measurements predicted it best. Weight, height, age and sex together explained about 71% of the variation. The coefficients above are the fitted values, and the sex term reflects that men carry more muscle at the same size.

The activity factors (1.2 for sedentary up to 1.9 for very active) come from studies that measured total daily energy use. They scale resting needs up to include everything you do in a day. They’re rougher than the BMR equation itself.

A 2005 systematic review compared the common equations and found Mifflin–St Jeor the most accurate, within 10% of the measured value for most people. It replaced the 1919 Harris–Benedict equation as the usual default.

Worked example

A 35-year-old woman, 165 cm, 65 kg, with light exercise:

$$\text{BMR} = 10(65) + 6.25(165) - 5(35) - 161 = 1345\ \text{kcal/day}$$ $$1345 \times 1.375 = 1850\ \text{kcal/day}$$

Watch out for

• It’s an estimate. Individuals vary by about ±10% around the prediction, sometimes more. Track your weight for a few weeks and adjust.
• The “500 kcal deficit” rule comes from the old estimate that a pound of fat stores about 3,500 kcal. Real weight loss slows as the body adapts, so treat it as a starting point.
• Very muscular or very lean people burn more than the equation predicts, since it doesn’t know your body composition.

Sources

• Mifflin, M. D. et al. (1990). A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition 51(2), 241–247.
• Frankenfield, D., Roth-Yousey, L. & Compher, C. (2005). Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. Journal of the American Dietetic Association 105(5), 775–789.

Last checked November 11, 2026