Health & fitness
Estimate resting daily energy needs from age, height, weight, and sex.
Enter your numbers to see the answer.
BMR calculator guide
Basal metabolic rate is the energy your body uses at complete rest to keep breathing, circulating blood, regulating temperature, and running your organs. This calculator estimates it with the Mifflin-St Jeor equation, which takes weight in kilograms, height in centimetres, age in years, and sex, and returns kilocalories per day. Mifflin-St Jeor was published in 1990 and, in a 2005 review by the Academy of Nutrition and Dietetics, predicted measured resting energy expenditure more accurately than the older Harris-Benedict equation in healthy adults, which is why most clinical and fitness tools now use it. BMR is the starting point for planning intake: multiply it by an activity factor, typically 1.2 for sedentary through 1.9 for very active, to estimate total daily energy needs. The equation was derived from healthy adults of normal to obese weight and is less reliable for children, athletes with very high muscle mass, pregnant women, and older adults. An estimate from a formula is a screening figure, not a diagnosis; measured metabolic testing or a dietitian is the route if the number matters clinically.
Mifflin-St Jeor BMR (kcal/day) = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + s, where s = +5 for males and −161 for females. The result is rounded to the nearest whole kilocalorie.
Worked example with the default inputs: a 30-year-old male weighing 70 kg and 170 cm tall. Weight term = 10 × 70 = 700. Height term = 6.25 × 170 = 1,062.5. Age term = 5 × 30 = 150. BMR = 700 + 1,062.5 − 150 + 5 = 1,617.5 kcal/day, which the calculator rounds to 1,618 kcal/day. The same weight, height, and age for a female uses −161 instead of +5: 700 + 1,062.5 − 150 − 161 = 1,451.5, displayed as 1,452 kcal/day. Multiplying 1,618 by a sedentary factor of 1.2 gives roughly 1,940 kcal/day of total energy need.
Weight is in kilograms and height in centimetres. To convert, divide pounds by 2.2046 (154 lb ≈ 70 kg) and multiply inches by 2.54 (5 ft 7 in = 67 in ≈ 170 cm). Age is in whole years. The output is kilocalories per day, the unit food labels in most countries call calories; to express it in kilojoules, multiply by 4.184. Weigh yourself in the morning before eating for a consistent input.
This is a screening figure, not a diagnosis. Population formulas do not account for build, muscle mass, age, pregnancy, ethnicity, or medical history, so an individual result can sit well outside the healthy band without indicating a problem, or inside it while one exists. Discuss anything that concerns you with a qualified clinician rather than acting on this number alone. On this page the figure rests entirely on weight, height, age and sex, so start there if the bmr calculator returns something you did not expect.
Good to know: BMR is not the number of calories to eat. Eating at BMR is a deficit for anyone who moves at all, because it omits activity and the energy used to digest food. Entering weight in pounds or height in inches without converting produces a result that is far too low or high; 170 in the height field means 170 cm. The sex constant reflects average body composition in the study population, so a very muscular person of either sex will usually have a higher true BMR than the formula predicts.
This is an educational screening estimate, not a diagnosis or a substitute for professional medical advice.
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How it works
Estimate resting daily energy needs from age, height, weight, and sex. This tool explains the calculation so you can adjust the assumptions to match your situation.
Worked example
With Weight = 70 kg · Height = 170 cm · Age = 30 · Sex = male → 1,618 kcal/day (estimated resting energy need). Change an input above and this example updates with your numbers.
Common questions
Multiply weight in kilograms by 10, add 6.25 times height in centimetres, subtract 5 times age in years, then add 5 if male or subtract 161 if female. A 70 kg, 170 cm, 30-year-old male gets 700 + 1,062.5 − 150 + 5 = 1,618 kcal/day.
For a 70 kg, 170 cm man aged 30 the Mifflin-St Jeor estimate is about 1,618 kcal/day. Taller or heavier men score higher; each extra kilogram adds 10 kcal and each extra centimetre adds 6.25. Typical adult male values fall between roughly 1,500 and 2,000 kcal/day.
BMR is energy used at complete rest. Total daily energy expenditure adds physical activity and the cost of digesting food. Multiply BMR by an activity factor: about 1.2 for desk work with little exercise, 1.375 for light activity, 1.55 for moderate, 1.725 for heavy, and 1.9 for very heavy training.
For most healthy adults, yes. The Academy of Nutrition and Dietetics review found Mifflin-St Jeor predicted measured resting metabolic rate within 10% in a larger share of people than the 1919 Harris-Benedict equation or its 1984 revision. Any equation can still miss by 200 kcal or more for an individual.
Generally not. BMR omits all activity, so eating at that level is usually a larger deficit than intended and hard to sustain. A more common approach is to estimate total daily energy needs, then reduce intake moderately. This estimate is for screening and planning only; a clinician or registered dietitian can advise on a personal target.