BMR Calculator

Basal Metabolic Rate is an estimate of the energy your body uses per day at complete rest. It represents essential functions such as breathing, circulation, cell maintenance, temperature regulation, and basic nervous system activity.

BMR is not a diagnosis and it is not a full daily calorie target. It is a resting estimate that can be useful as a starting point for understanding energy needs.

1. Choose Metric Units, US Units, or Other Units.
2. Enter age, gender or sex, height, and weight.
3. Add body fat percentage only if you want Katch-McArdle.
4. Select Calculate to see the main BMR estimate and comparisons.
5. Use Copy, Print, or Share when you want to save the result.

NexaCalc converts all inputs to kilograms and centimeters before applying the equations.

Mifflin-St Jeor is the default method on this page because it is a common practical equation for estimating resting energy expenditure from age, sex, height, and weight.

The Revised Harris-Benedict equation is shown as a comparison result. It uses a different coefficient set, so it can produce a higher or lower estimate than Mifflin-St Jeor for the same person.

Katch-McArdle uses lean body mass instead of separate male and female constants. NexaCalc only shows it when body fat percentage is entered.

Metric example: male, age 30, 70 kg, 175 cm. Mifflin-St Jeor is 10 x 70 + 6.25 x 175 - 5 x 30 + 5 = 1648.75 kcal/day, rounded to 1,649 kcal/day.

US example: female, age 35, 150 lb, 5 ft 5 in. The inputs convert to about 68.04 kg and 165.1 cm. Mifflin-St Jeor is approximately 1,376 kcal/day after rounding.

BMR estimates resting calorie use. TDEE estimates total daily energy use after activity, steps, exercise, digestion, and normal movement are included. For day-to-day calorie planning, TDEE is usually more useful than BMR alone.

For a dedicated activity-based estimate, use the TDEE Calculator.

BMR and RMR both describe resting energy use, but BMR is often associated with stricter measurement conditions. RMR is commonly used in practical settings and may be slightly different because conditions are less restrictive.

Body size, lean mass, age, genetics, hormones, health status, sleep, stress, and measurement conditions can all affect resting energy use. Two people with the same height and weight can still have different measured energy expenditure.

A BMR calculator is an estimate. Formulas may be less accurate for very muscular people, very lean people, people with obesity, pregnant users, highly trained athletes, people with medical conditions, and children or teens.

BMR can help explain the resting part of energy use, but it does not promise weight loss or any health outcome. Food intake, activity, consistency, medical context, and personal preferences all matter when planning nutrition.

The Mifflin-St Jeor and Harris-Benedict equations use different constants for male and female inputs. These constants reflect average differences in the datasets used to build the formulas, not a personalized measurement of metabolism.

BMR equations on this page are adult-style estimates. For children and teens, energy needs should be interpreted with growth, puberty, activity, and clinical context in mind.

Formulas cannot see body composition, thyroid status, medications, illness, pregnancy, training load, or lab measurement conditions. They are useful planning estimates, not clinical measurements.

• Mifflin MD, St Jeor ST, Hill LA, Scott BJ, Daugherty SA, Koh YO. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition, 1990.
• Harris JA, Benedict FG. A Biometric Study of Human Basal Metabolism in Man. Carnegie Institution of Washington, 1919.
• Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. American Journal of Clinical Nutrition, 1984.
• Katch VL, McArdle WD, Katch FI. Exercise physiology and body composition references used for lean-mass-based energy estimates.
• National Academies Dietary Reference Intakes: general energy expenditure and nutrition planning context.
• CDC and NIH-style public health resources: general healthy weight and energy balance context.