BMR Calculator – Basal Metabolic Rate
By Talcart · Last updated July 10, 2026
BMR Calculator Guide
Understanding BMR
Available Formulas
Mifflin-St Jeor: Most accurate for most people
Harris-Benedict: Traditional formula
Katch-McArdle: Best when body fat % is known
Factors Affecting BMR
Age: BMR decreases with age
Gender: Men typically have higher BMR
Body composition: More muscle = Higher BMR
Genetics and health conditions
BMR Calculator – Basal Metabolic Rate
This BMR calculator computes the calories your body burns at complete rest — for a 40-year-old man of 180 cm and 80 kg, that is 1,730 kcal per day using the Mifflin-St Jeor equation. Enter your sex, age, height, and weight to get your Basal Metabolic Rate, the foundation for setting maintenance, weight-loss, or muscle-gain calorie targets.
Key facts
- Mifflin-St Jeor equation: BMR = 10W + 6.25H - 5A + 5 (men) or - 161 (women), with weight in kg, height in cm, age in years (Mifflin et al., 1990).
- BMR typically accounts for 60-75% of total daily energy expenditure in adults.
- A 2005 American Dietetic Association review (Frankenfield et al.) found Mifflin-St Jeor the most reliable common prediction equation, more often within 10% of measured resting metabolic rate than Harris-Benedict.
- TDEE = BMR x activity factor, with standard multipliers from 1.2 (sedentary) to 1.9 (extremely active).
What is the BMR Calculator?
Basal Metabolic Rate (BMR) is the number of kilocalories the body requires over 24 hours to sustain vital functions — breathing, circulation, cell production, and temperature regulation — while at complete physical and digestive rest. BMR typically accounts for 60-75% of total daily energy expenditure, making it the largest single component of the calories you burn. It is determined mainly by body size, lean muscle mass, age, and sex. Because measuring BMR directly requires laboratory calorimetry, calculators estimate it with validated prediction equations such as Mifflin-St Jeor.
How does the BMR Calculator work?
The calculator applies the Mifflin-St Jeor equation, published in 1990 and regarded as the most reliable prediction formula for the general population: BMR = 10 x weight (kg) + 6.25 x height (cm) - 5 x age (years) + 5 for men, and the same expression - 161 for women. The older Harris-Benedict equation (1919, revised 1984) uses different coefficients and tends to estimate slightly higher. To turn BMR into a full daily calorie target, multiply by an activity factor between 1.2 (sedentary) and 1.9 (extremely active).
What is the BMR Calculator formula?
- w – weight (kg)
- h – height (cm)
- a – age (years)
Mifflin-St Jeor worked examples (BMR in kcal/day, exact values)
| Profile | Calculation | BMR |
|---|---|---|
| Man, 25 y, 175 cm, 70 kg | 700 + 1,093.75 - 125 + 5 | 1,674 kcal |
| Woman, 25 y, 162 cm, 58 kg | 580 + 1,012.5 - 125 - 161 | 1,307 kcal |
| Man, 40 y, 180 cm, 80 kg | 800 + 1,125 - 200 + 5 | 1,730 kcal |
| Woman, 40 y, 165 cm, 65 kg | 650 + 1,031.25 - 200 - 161 | 1,320 kcal |
| Man, 60 y, 172 cm, 75 kg | 750 + 1,075 - 300 + 5 | 1,530 kcal |
| Woman, 60 y, 158 cm, 62 kg | 620 + 987.5 - 300 - 161 | 1,147 kcal |
How do you use the BMR Calculator?
- Select your sex.
- Enter age, height (cm), and weight (kg).
- Read your BMR – the minimum calories your body burns at rest.
Worked example
| Scenario | 40-year-old man, 180 cm, 80 kg |
| Calculation | BMR = 10(80) + 6.25(180) − 5(40) + 5 = 800 + 1125 − 200 + 5 = 1730 kcal |
| Result | BMR ≈ 1,730 kcal/day at complete rest. |
Common use cases
Tips & best practices
BMR drops slightly with age — about 1–2% per decade after 20.
Strength training is the most effective way to maintain BMR as you age.
Frequently asked questions
Most adult women have a BMR of roughly 1,200-1,600 kcal/day and most adult men roughly 1,500-2,000 kcal/day, though the number depends heavily on size, age, and muscle mass. By Mifflin-St Jeor, a 30-year-old woman of 162 cm and 58 kg has a BMR of about 1,282 kcal, while a 30-year-old man of 180 cm and 85 kg has about 1,830 kcal. There is no single "good" BMR — it simply reflects your body's resting energy needs.
Use the Mifflin-St Jeor equation: multiply your weight in kg by 10, add 6.25 times your height in cm, subtract 5 times your age in years, then add 5 if male or subtract 161 if female. Example: a 25-year-old woman, 162 cm, 58 kg gives 580 + 1,012.5 - 125 - 161 = 1,306.5, so about 1,307 kcal per day at complete rest.
BMR is the energy your body uses at complete rest; TDEE (Total Daily Energy Expenditure) adds everything else — daily movement, exercise, and the energy cost of digesting food. TDEE is calculated as BMR times an activity factor from 1.2 (sedentary) to 1.9 (extremely active). Calorie targets for losing or gaining weight should be set against TDEE, not BMR, since almost no one burns only their BMR in a real day.
Yes, for most adults. A systematic review by the American Dietetic Association (Frankenfield et al., 2005) found the Mifflin-St Jeor equation predicted measured resting metabolic rate within 10% of the true value more often than the Harris-Benedict and other common equations, in both normal-weight and obese adults. Harris-Benedict, published in 1919, tends to overestimate slightly, which is why Mifflin-St Jeor is the modern default.
Modestly, yes. Building lean muscle through resistance training raises resting energy use, since muscle tissue burns more calories at rest than fat tissue. Adequate protein intake and avoiding prolonged very-low-calorie diets help preserve the muscle that supports your BMR. Age-related decline is normal — resting metabolism falls gradually through adulthood — but strength training is the most effective countermeasure. Claims that specific foods dramatically boost metabolism are not well supported.
Generally no. A sensible deficit is taken from TDEE, not BMR — eating 500 kcal below TDEE typically produces about 1 lb (0.45 kg) of loss per week while still covering resting needs. Routinely eating below BMR is not automatically dangerous, but it makes adequate nutrition hard to achieve and often costs muscle mass. If your calculated targets fall below your BMR, consult a healthcare provider or registered dietitian first.
Yes. In the Mifflin-St Jeor equation, each year of age reduces predicted BMR by 5 kcal/day — about 50 kcal per decade — mainly because lean muscle mass declines over time. For example, the equation gives an 80 kg, 180 cm man a BMR of 1,805 kcal at age 25 but 1,630 kcal at age 60. Regular resistance training slows this decline by preserving muscle.