Basal metabolic rate (BMR) is the number of calories your body burns at complete rest. The Mifflin–St Jeor equation, the most accurate for healthy adults, is 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 for men, or − 161 for women. A 35-year-old woman of 5 ft 5 in and 150 lb has a BMR of about 1,376 calories a day; multiplied by an activity factor, that gives her daily total.
Enter your details for your BMR by three equations and the calories you burn in a day at each activity level.
Worked example
Sex: FemaleAge: 35 yearsHeight: 5 ft 5 inWeight: 150 lb
BMR (Mifflin–St Jeor): 1,376 kcal/day
A 35-year-old woman of 5 ft 5 in and 150 lb burns about 1,376 calories a day at rest by Mifflin–St Jeor. Lightly active, her whole day comes to about 1,890 calories.
Open this example in the calculator →How to use the BMR Calculator
- Choose your sex and enter your age.
- Choose US or metric units and enter your height and weight.
- Optionally add your body fat percentage for the Katch–McArdle equation.
- Read your BMR and the daily calories for each activity level.
The BMR equations
- Mifflin–St Jeor (1990): men 10W + 6.25H − 5A + 5; women 10W + 6.25H − 5A − 161 (W kg, H cm, A years).
- Harris–Benedict, revised by Roza and Shizgal (1984): men 88.362 + 13.397W + 4.799H − 5.677A; women 447.593 + 9.247W + 3.098H − 4.330A.
- Katch–McArdle: 370 + 21.6 × lean body mass (kg). It uses body composition instead of sex and age, so it suits people who know their body fat — especially athletes.
Worked through: a woman of 35, 165 cm and 68 kg: 680 + 1,031.9 − 175 − 161 = 1,376 kcal. A 2005 review by the American Dietetic Association found Mifflin–St Jeor predicted measured resting energy within 10% for more people than any other equation, which is why it is the default here.
Activity factors
| Activity level | Description | Multiply BMR by |
|---|---|---|
| Sedentary | Little or no exercise, desk job | 1.2 |
| Lightly active | Light exercise 1–3 days a week | 1.375 |
| Moderately active | Moderate exercise 3–5 days a week | 1.55 |
| Very active | Hard exercise 6–7 days a week | 1.725 |
| Extra active | Physical job plus hard training | 1.9 |
Most people overestimate their activity. If you are unsure, choose the lower level and adjust after a few weeks of watching your weight.
BMR, RMR and TDEE
BMR is measured in strict conditions: lying down, fasted, after a night’s sleep. Resting metabolic rate (RMR) is measured more loosely and runs a little higher; the two are often used interchangeably, and Mifflin–St Jeor actually predicts RMR. Total daily energy expenditure (TDEE) adds everything else — digesting food (about 10%), exercise and everyday movement. TDEE is the number to plan meals around; the calorie calculator works it out with goals for losing or gaining weight.
Can you raise your BMR?
Modestly. Muscle burns more energy than fat at rest, so strength training that adds muscle raises BMR a little — on the order of tens of calories a day per few pounds of muscle. Very low-calorie diets lower it, which is one reason crash diets stall. Age lowers it by roughly 1 to 2% a decade after early adulthood, mostly through muscle loss.
Frequently asked questions
What is a normal BMR?
For adults, roughly 1,200 to 1,500 calories a day for women and 1,500 to 1,900 for men, depending mostly on body size, age and muscle. Your result above is the best estimate for you.
What is the most accurate BMR formula?
For healthy adults, Mifflin–St Jeor: in a 2005 review it came within 10% of measured resting energy for more people than other equations. If you know your body fat, Katch–McArdle can be better, especially for lean, muscular people.
How do I calculate my BMR?
With Mifflin–St Jeor: 10 × weight in kg + 6.25 × height in cm − 5 × age, then add 5 for men or subtract 161 for women.
Is BMR the same as the calories I need?
No. BMR is only what you burn at rest. Multiply it by an activity factor — 1.2 if sedentary up to 1.9 if very active — to estimate the calories you need in a day.
Should I eat below my BMR to lose weight?
Usually not. Aim for a deficit from your total daily calories (TDEE) instead, typically 250 to 500 calories a day. Eating below BMR for long risks muscle loss and nutrient shortfalls, and makes the diet hard to keep up.
Why does BMR decrease with age?
Mostly because muscle mass falls with age, and muscle uses more energy than fat. Staying active and doing strength training slows the decline.
Sources
- Mifflin MD et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51:241–247 — American Journal of Clinical Nutrition
- Frankenfield D, Roth-Yousey L, Compher C. Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults: a systematic review. J Am Diet Assoc 2005;105:775–789 — Journal of the American Dietetic Association
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated. Am J Clin Nutr 1984;40:168–182 — American Journal of Clinical Nutrition
- Dietary Guidelines for Americans, 2020–2025 — U.S. Department of Agriculture and HHS
- Body Weight Planner — National Institute of Diabetes and Digestive and Kidney Diseases (NIH)
- Hall KD et al. Quantification of the effect of energy imbalance on bodyweight. Lancet 2011;378:826–837 — The Lancet
For general information only — not a diagnosis or a substitute for advice from a doctor. How we calculate.