BMR Calculator
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Estimated BMR 1,392 kcal/day by Mifflin–St Jeor and 1,445 kcal/day by revised Harris–Benedict.
- Mifflin–St Jeor
- 1,392
- Revised Harris–Benedict
- 1,445
BMR is the energy you would use lying at complete rest for a day. It is not the number of calories to eat: multiply it by your activity level in the TDEE or calorie calculator for that.
This is an estimate from a published formula, not medical advice. Talk to a doctor or registered dietitian about your own situation.
How to use the BMR calculator
- Choose US or metric units and enter your sex, age, height and weight.
- Add your body fat percentage if you know it, to see the Katch–McArdle estimate as well.
- Compare the formulas. The spread between them is a reminder that each one is an estimate, not a measurement.
BMR formulas
Revised Harris–Benedict: men 88.362 + 13.397W + 4.799H − 5.677A
women 447.593 + 9.247W + 3.098H − 4.330A
Katch–McArdle: 370 + 21.6 × LBM, where LBM = W × (1 − body fat % ÷ 100)
kJ = kcal × 4.184
W is weight in kilograms, H is height in centimeters, A is age in years and LBM is lean body mass in kilograms. Mifflin–St Jeor was fitted in 1990 to calorimetry measurements from 498 healthy adults, both normal-weight and obese. The Harris–Benedict equations date from 1919 and were refitted by Roza and Shizgal in 1984. Katch–McArdle ignores age and sex and works from lean mass alone, so it is only as good as your body-fat figure.
Worked example
A 30-year-old man who is 180 cm tall and weighs 80 kg has a Mifflin–St Jeor BMR of 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 1,780 kcal a day, or 7,448 kJ. The revised Harris–Benedict equation gives 1,854 kcal. At 20% body fat his lean mass is 64 kg, so Katch–McArdle gives 370 + 21.6 × 64 = 1,752 kcal. The three results span 101 kcal, a reminder that each formula is an estimate.
BMR by age
How the two sex-specific equations change with age for a woman 5 ft 5 in and 140 lb and a man 5 ft 10 in and 180 lb, holding weight and height constant. Mifflin–St Jeor drops by exactly 5 kcal a day for each year of age.
| Age | Woman, Mifflin | Woman, Harris–Benedict | Man, Mifflin | Man, Harris–Benedict |
|---|---|---|---|---|
| 20 | 1,406 | 1,460 | 1,833 | 1,922 |
| 30 | 1,356 | 1,416 | 1,783 | 1,865 |
| 40 | 1,306 | 1,373 | 1,733 | 1,808 |
| 50 | 1,256 | 1,330 | 1,683 | 1,752 |
| 60 | 1,206 | 1,286 | 1,633 | 1,695 |
| 70 | 1,156 | 1,243 | 1,583 | 1,638 |
Which formula should you use?
- Mifflin–St Jeor is the default. In a 2005 systematic review in the Journal of the American Dietetic Association, it estimated resting energy within 10% of the measured value in more people than any other common equation.
- Revised Harris–Benedict is still widely used and tends to come out a little higher. Mifflin's study found the original equations overestimated measured resting energy by about 5%.
- Katch–McArdle suits people who know their body fat from a reliable method, such as athletes with a DXA scan. A tape or bathroom-scale estimate adds its own error.
What BMR does and doesn't tell you
Your BMR is not how much to eat. It leaves out everything you do in a day, from walking around to exercise and digesting food. Multiply it by an activity factor in the TDEE calculator, or go straight to a daily target with the calorie calculator. Strictly, these equations predict resting energy expenditure, measured lying quietly after a night's fasting; the terms BMR and RMR are often used interchangeably. Lean mass, body size, age and sex explain most of the difference between people, but genetics, hormones such as thyroid hormone, illness and some medicines also play a part, so a measured value from indirect calorimetry can differ from every formula. If you need a precise figure for medical reasons, ask your doctor about measurement. To estimate body fat for Katch–McArdle, try the body fat calculator.
This is not medical advice; talk to a doctor or registered dietitian.
Sources
- Mifflin MD, St Jeor ST, et al. A new predictive equation for resting energy expenditure in healthy individuals. Am J Clin Nutr 1990;51(2):241–247.
- Roza AM, Shizgal HM. The Harris Benedict equation reevaluated: resting energy requirements and the body cell mass. Am J Clin Nutr 1984;40(1):168–182.
- McArdle WD, Katch FI, Katch VL. Exercise Physiology: Nutrition, Energy, and Human Performance (Katch–McArdle equation).
- 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(5):775–789.
Frequently asked questions
What is BMR?
Basal metabolic rate is the energy your body uses in a day at complete rest, to keep your heart beating, lungs breathing, brain working and body warm. For most people it is the largest part of daily energy use. A 35-year-old woman who is 5 ft 5 in and 140 lb has a Mifflin–St Jeor BMR of about 1,331 kcal a day.
How do I calculate my BMR?
With the Mifflin–St Jeor equation: 10 × weight in kg + 6.25 × height in cm − 5 × age, then add 5 for men or subtract 161 for women. A 30-year-old man who is 180 cm and 80 kg has a BMR of 800 + 1,125 − 150 + 5 = 1,780 kcal a day, or about 7,448 kJ.
Why do the BMR formulas give different results?
They were fitted to different groups of people at different times. For the 80 kg man above, Mifflin–St Jeor gives 1,780 kcal, the revised Harris–Benedict equation 1,854 kcal and, at 20% body fat, Katch–McArdle 1,752 kcal. Mifflin–St Jeor was the most reliable in a 2005 systematic review.
Does BMR go down with age?
In the formulas, yes: Mifflin–St Jeor subtracts 5 kcal a day for each year, so for a woman who is 5 ft 5 in and 140 lb it falls from about 1,356 kcal at 30 to 1,206 kcal at 60. Part of the real-life decline comes from losing muscle, which regular strength training can help limit.
Is BMR the number of calories I should eat?
No. BMR leaves out all movement, exercise and digestion. Multiply it by an activity factor (from 1.2 for sedentary to 1.9 for very hard training) to estimate your daily needs, as the TDEE and calorie calculators do. The calorie calculator also flags targets below the commonly cited minimums of 1,200 kcal a day for women and 1,500 for men.