BMR Calculator

Calculate your Basal Metabolic Rate and daily calorie needs.

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Results

Basal Metabolic Rate

cal/per day

Daily Calories at Rest 0 cal

Adjusted Calories (with activity) 0 cal

About BMR Calculation

Your Basal Metabolic Rate (BMR) is the number of calories your body needs to accomplish its most basic life-sustaining functions, such as breathing, circulation, and cell production.

The Mifflin-St Jeor equation used here is considered the most accurate method for estimating BMR in most adults.

Frequently Asked Questions

What is BMR?

BMR (Basal Metabolic Rate) is the number of calories your body burns at rest to maintain basic life functions like breathing, circulation, and cell production.

How is BMR calculated?

This calculator uses the Mifflin-St Jeor equation, which is considered one of the most accurate BMR formulas for most people.

What affects BMR?

BMR is affected by age, gender, weight, height, and body composition. Muscle mass particularly increases BMR since muscle burns more calories than fat.

Basal Metabolic Rate (BMR) is the number of calories the body burns at complete rest, just to keep the heart beating, the lungs breathing, the brain running, and body temperature stable. It is the largest slice of daily energy expenditure for most people, usually 60 to 75 percent of total calories burned. The remainder comes from the thermic effect of food (digesting what is eaten) and physical activity. BMR is not the same as what a person burns in a normal day, but it is the foundation on top of which an activity-adjusted estimate is built.

Several formulas estimate BMR from age, sex, height, and weight. The Mifflin-St Jeor equation, published in 1990, is now the most widely recommended by the American Dietetic Association and is the formula used in most clinical and research settings. It tends to predict BMR within about 10 percent for most people, which is more accurate than the older Harris-Benedict equation it replaced. The Katch-McArdle formula goes a step further by using lean body mass, which is useful for athletes and very lean individuals, but it requires knowing body fat percentage, which most people do not have on hand.

BMR is often confused with TDEE (Total Daily Energy Expenditure). TDEE multiplies BMR by an activity factor: 1.2 for sedentary, 1.375 for lightly active, 1.55 for moderately active, 1.725 for very active, and 1.9 for extra active (manual labor or twice-daily training). TDEE is the number to use when planning calorie intake for weight maintenance, loss, or gain. BMR is the number to use when figuring out the floor below which calorie intake should not go without medical supervision, since eating significantly below BMR for extended periods slows metabolism, hormone production, and lean mass.

The most common use of BMR is to size a calorie target. A typical fat-loss plan sets intake about 15 to 25 percent below TDEE (not below BMR), while a lean bulk sits 5 to 15 percent above TDEE. The NIH, the CDC, and the Academy of Nutrition and Dietetics all recommend not going below about 1,200 kcal/day for women or 1,500 kcal/day for men without medical supervision. For weight loss specifically, the CDC and the American Heart Association suggest a steady deficit of 500 to 750 kcal/day as a sustainable rate, which lines up with about 0.5 kg (1 lb) of weight loss per week.

How to use

Enter sex, age (years), height (cm or inches), and weight (kg or lb) into the form.
Submit to see the BMR in calories per day, the activity-adjusted TDEE, and the recommended intake ranges for weight loss, maintenance, or gain.
Choose the activity level that best matches the average week, not the best or worst day. A 'lightly active' office worker who walks 30 minutes a day, three times a week, is closer to 1.375 than to 1.55.
Recalculate every 4 to 6 weeks as weight changes, since BMR is a function of current body mass.

Formula

Mifflin-St Jeor (men): BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161 + 166. (Women): BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161. TDEE = BMR × activity factor (1.2 to 1.9).

Interpreting your results

A BMR between 1,200 and 1,800 kcal/day is typical for adult women, and 1,500 to 2,200 for adult men, with significant variation by body size. A very low BMR (below 1,200 for women or 1,500 for men) usually reflects low lean mass, very low calorie intake, or both, and is worth discussing with a clinician. A high BMR (above 2,000 for women or 2,500 for men) is common in larger or very active people and is not a sign of a problem on its own. The CDC and NIH use BMR-derived TDEE as the starting point for medically supervised weight management, and a registered dietitian can refine the estimate using body composition data.

Frequently asked questions

What is the difference between BMR and TDEE?

BMR is what the body burns at complete rest. TDEE includes BMR plus the thermic effect of food and all physical activity, and is calculated as BMR × activity factor (1.2 to 1.9). TDEE is the right number for calorie planning, while BMR is the floor below which intake should not go without medical supervision.

Which formula is most accurate?

Mifflin-St Jeor is the most accurate equation that uses only height, weight, age, and sex, and is the formula recommended by the Academy of Nutrition and Dietetics. Katch-McArdle is more accurate when lean body mass is known. The older Harris-Benedict equation tends to over-predict BMR by 5 to 15 percent in modern populations.

Does BMR decrease with age?

Yes. BMR peaks in late adolescence and early adulthood, then drops roughly 1 to 2 percent per decade after age 20, mostly because of loss of lean muscle mass. The Mifflin-St Jeor formula captures the age component directly, and resistance training can slow the decline by preserving lean tissue, as the NIH notes in its physical activity guidelines.

Should I eat below my BMR to lose weight faster?

Not without medical supervision. The Academy of Nutrition and Dietetics and the CDC recommend a moderate deficit of about 500 to 750 kcal/day below TDEE, not below BMR. Going well below BMR for weeks can drop thyroid output, suppress reproductive hormones, and cost lean mass along with fat.