BMR Calculator
This BMR calculator estimates your basal metabolic rate, the calories your body uses at complete rest, with the Mifflin–St Jeor equation. Enter your sex, age, height and weight; it works in US or metric units.
Result
1,676 calories/day
| Basal metabolic rate (Mifflin–St Jeor) | 1,676 kcal/day |
|---|---|
| In kilojoules | 7,013 kJ/day |
| Per hour at rest | 70 kcal |
Calories your body uses at complete rest. Daily needs are higher once activity is included.
What Is Basal Metabolic Rate?
Your body uses energy all the time, even when you’re lying completely still. Breathing, pumping blood, keeping warm and running your organs all take fuel. Basal metabolic rate (BMR) estimates that baseline in calories per day.
BMR is the starting point for working out daily calorie needs. Activity and digestion add to it, which is why the figure from our calorie calculator is always higher.
The Mifflin–St Jeor Equation
The calculator uses the equation published by Mifflin, St Jeor and colleagues in 1990. They measured the resting energy expenditure of 498 healthy adults and fitted a formula to the results:
Men: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5
Women: BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161
The result is in kilocalories (the “calories” on food labels) per day.
Converting US units
- Weight in kg = pounds × 0.4536
- Height in cm = inches × 2.54
Worked Example
A 30-year-old man who is 5 ft 9 in tall and weighs 160 lb:
- Weight: 160 × 0.4536 = 72.57 kg
- Height: 69 in × 2.54 = 175.26 cm
- 10 × 72.57 = 725.75
- 6.25 × 175.26 = 1,095.38
- 5 × 30 = 150
- BMR = 725.75 + 1,095.38 − 150 + 5 = 1,676 calories/day
A woman with the same age, height and weight would get 1,676 − 166 = 1,510 calories/day, because her constant is −161 rather than +5.
What Changes BMR in the Equation
| Change | Effect on the estimate |
|---|---|
| +1 kg (2.2 lb) body weight | +10 calories/day |
| +1 cm (0.39 in) height | +6.25 calories/day |
| +1 year of age | −5 calories/day |
Weight and height have the largest effect, so the estimate changes most when body size changes.
Using the Result
BMR isn’t a calorie target
BMR describes the body at complete rest. It isn’t a recommended amount to eat. Daily energy needs include activity on top of BMR. For a figure that accounts for activity, use the calorie calculator, which uses the Institute of Medicine’s Estimated Energy Requirement equations.
Measurements matter
The equation depends on accurate weight and height. Weigh and measure without shoes, and use your current weight rather than a goal weight.
It’s an average, not a measurement
The equation predicts what’s typical for people with your measurements. Two people with identical numbers can have different resting energy use, depending on factors the equation doesn’t include, such as body composition. The body fat calculator estimates body composition from tape measurements.
When to ask a professional
For medical conditions, pregnancy, or planning major changes to diet or weight, a doctor or registered dietitian can give guidance for your situation. This calculator gives a general estimate only.
Frequently Asked Questions
What is BMR?
Basal metabolic rate is the energy your body uses at complete rest to keep breathing, circulating blood and maintaining body temperature. It's the baseline before any physical activity or digestion is counted.
What is the Mifflin–St Jeor equation?
It's a formula published in 1990 in the American Journal of Clinical Nutrition that predicts resting energy expenditure from weight, height, age and sex. For men it is 10 × weight in kg + 6.25 × height in cm − 5 × age + 5; for women the final term is −161 instead of +5.
What's the difference between BMR and daily calorie needs?
BMR covers only the body at rest. Daily calorie needs add everything else, including movement, exercise and digesting food, so they are higher. Our calorie calculator estimates total daily needs from activity level.
Why does BMR go down with age?
In the Mifflin–St Jeor equation, each year of age lowers the estimate by 5 calories a day, all else being equal. Weight and height carry more weight in the equation, so changes in body size usually matter more than age.
How accurate is a BMR calculator?
It's an estimate from a regression equation built on measurements of 498 healthy adults aged 19 to 78. Individual results vary, and the only way to measure resting energy expenditure precisely is with laboratory equipment such as indirect calorimetry.
Why does the equation ask for sex?
The study that produced the equation found different average resting energy expenditure for men and women with the same weight, height and age. The equation adjusts for this with a separate constant.
Related Calculators
- Calorie CalculatorDaily calories to maintain weight, at four activity levels.
- BMI CalculatorBody mass index, CDC weight category and healthy weight range.
- Ideal Weight CalculatorHealthy weight range for your height, plus four classic formulas.
- Body Fat CalculatorBody fat percentage from tape measurements (U.S. Navy method).
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.
- The equation was derived from 498 healthy adults (247 women, 251 men) aged 19–78; this calculator accepts ages 19 and over.
- Results are rounded to whole calories for display only.
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