BMR Calculator
Estimate how many calories your body burns at rest so you have a physiological baseline before factoring in activity and nutrition goals.
How to use this BMR calculator
- Select sex
Choose male or female to apply the correct equation constant.
- Enter age
Enter your age in years in the age field.
- Enter weight
Enter your body weight in the weight field.
- Enter height
Enter your standing height in the height field.
- Review results
Check your estimated daily and hourly resting calorie burn.
How this BMR calculator works
This BMR calculator estimates resting calorie needs — the number of calories your body requires at rest to sustain basic physiological functions like breathing, circulation, cell production, and temperature regulation. The estimate uses the Mifflin-St Jeor equation. Technically, equations like Mifflin-St Jeor estimate resting energy expenditure more directly than laboratory basal metabolic rate, but consumers often search for this kind of estimate under the shorthand 'BMR.' Understanding the result gives you a physiological floor: real daily calorie needs will always be higher once physical activity is included.
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 Men: BMR = 4.536 × weight (lb) + 15.88 × height (in) − 5 × age (years) + 5
Women: BMR = 4.536 × weight (lb) + 15.88 × height (in) − 5 × age (years) − 161 A 30-year-old male who weighs 80 kg and is 178 cm tall would estimate BMR as: 10 × 80 + 6.25 × 178 − 5 × 30 + 5 = 800 + 1,112.5 − 150 + 5 = 1,767.5 kcal/day. That means his body needs roughly 1,768 calories per day just to maintain organ function and body temperature at complete rest.
A 30-year-old male who weighs 176 lb and is 70 in tall would estimate BMR as: 4.536 × 176 + 15.88 × 70 − 5 × 30 + 5 = 798 + 1,112 − 150 + 5 = 1,765 kcal/day. That means his body needs roughly 1,765 calories per day just to maintain organ function and body temperature at complete rest.
A 25-year-old female who weighs 60 kg and is 165 cm tall would estimate BMR as: 10 × 60 + 6.25 × 165 − 5 × 25 − 161 = 600 + 1,031.25 − 125 − 161 = 1,345 kcal/day. That figure represents her resting calorie needs before any physical activity is factored in.
A 50-year-old male who weighs 95 kg and is 175 cm tall would estimate BMR as: 10 × 95 + 6.25 × 175 − 5 × 50 + 5 = 950 + 1,093.75 − 250 + 5 = 1,799 kcal/day. Despite the higher body weight, the age coefficient pulls the estimate down compared to a younger person with the same measurements.
- ✓ The Mifflin-St Jeor equation was developed from a study of adults with a wide BMI range and is considered more accurate than the older Harris-Benedict equation for most people.
- ✓ BMR represents complete rest in a thermoneutral environment — it does not include the thermic effect of food or any physical movement.
- ✓ The equation uses total body weight, not lean mass, so very muscular or very lean individuals may see a less accurate estimate.
- ✓ Results are statistical averages; individual metabolic variation of 5–10% is normal even among people with identical inputs.
- BMR naturally declines with age and lower body weight, which is one reason calorie needs shift over time even without changes in activity.
- If you have a very high or very low body-fat percentage, equations that factor in lean body mass (like Katch-McArdle) may give a more relevant estimate.
- BMR is a resting figure — to estimate total daily calorie needs, multiply BMR by an activity factor using a TDEE calculator.
- Mifflin, M.D. et al., 'A New Predictive Equation for Resting Energy Expenditure in Healthy Individuals,' American Journal of Clinical Nutrition, 1990
- Frankenfield, D. et al., 'Comparison of Predictive Equations for Resting Metabolic Rate in Healthy Nonobese and Obese Adults,' Journal of the American Dietetic Association, 2005
- Academy of Nutrition and Dietetics, Evidence Analysis Library — Energy Expenditure
What is basal metabolic rate?
Basal metabolic rate is the number of calories your body needs each day just to keep basic life-sustaining functions running — breathing, circulating blood, maintaining body temperature, producing cells, and supporting brain activity. It represents the energy cost of being alive at complete rest in a thermoneutral environment, with no food digestion or physical movement contributing to the total. For most people BMR accounts for roughly 60 to 70 percent of total daily calorie expenditure, making it by far the largest single component. The Mifflin-St Jeor equation estimates this value from weight, height, age, and sex because those variables correlate strongly with lean mass and organ size, both of which drive resting energy needs. Knowing your approximate BMR gives you a physiological floor: any activity, from walking to intense training, adds calories on top of this baseline.
Using your BMR estimate in practice
A BMR number on its own is not an intake target — eating exactly at BMR would leave you in a deficit because it does not account for any daily movement or the energy cost of digesting food. The most common practical use is to multiply BMR by an activity factor to estimate total daily energy expenditure, which then serves as the starting point for calorie planning. If your goal is fat loss, you would set intake moderately below that total; for muscle gain, moderately above it. Tracking your actual body-weight trend over two to four weeks alongside your intake tells you whether the estimate was close or needs adjustment. Because BMR declines gradually with age and with reductions in body weight, it is worth recalculating periodically — especially after significant weight change — rather than relying on a single estimate indefinitely.
BMR calculator FAQs
What is the difference between BMR and RMR?
BMR (basal metabolic rate) is measured under strict resting conditions, while RMR (resting metabolic rate) is measured under slightly less controlled conditions. In practice, predictive equations like Mifflin-St Jeor estimate a value very close to RMR, and the two terms are often used interchangeably.
Why does this calculator use the Mifflin-St Jeor equation?
Multiple validation studies have found Mifflin-St Jeor to be more accurate than the older Harris-Benedict equation across a broader range of body weights and compositions.
Can I eat only my BMR calories and lose weight?
Eating at BMR would put you in a deficit because your real daily expenditure includes movement and digestion on top of BMR. However, eating below BMR for extended periods is generally not recommended without medical supervision.
Does muscle mass affect BMR?
Yes. Muscle tissue is more metabolically active than fat tissue, so people with more lean mass tend to have a higher BMR even at the same total body weight.
Why does BMR decrease with age?
Aging is associated with gradual loss of lean tissue and hormonal changes that lower resting energy expenditure, which is reflected in the age coefficient in the equation.