The BMR Calculator estimates your Basal Metabolic Rate - the number of calories your body burns at complete rest. Enter your details below to see your BMR and your daily calorie needs at different activity levels.
The BMR calculator estimates your Basal Metabolic Rate - the number of calories your body burns at complete rest just to keep you alive. Even if you spent an entire day lying perfectly still, your body would still use this energy to power your heart, lungs, brain, kidneys, and the countless chemical reactions that sustain life. BMR is the foundation of every calorie and nutrition plan: it is the largest component of the calories you burn each day, and knowing it is the first step to understanding how much you should eat to lose, maintain, or gain weight. Enter your age, gender, height, and weight above to see your BMR and your estimated daily calorie needs at different activity levels.
Basal Metabolic Rate is the minimum amount of energy your body requires to maintain its vital functions while at rest. It represents the calories needed for involuntary activities such as breathing, circulating blood, regulating body temperature, growing and repairing cells, and keeping the brain and nervous system running. A useful analogy is the fuel an idling car burns while parked: the engine is on and consuming gas even though the car is not going anywhere. For most people, BMR accounts for roughly 60-70% of total daily energy expenditure, making it by far the biggest piece of the calorie puzzle.
Because BMR is measured under very strict conditions - complete rest, no recent meals, and a neutral temperature - it is the baseline from which all other calorie needs are calculated. Add the energy you use for digestion, daily movement, and exercise on top of BMR and you get your Total Daily Energy Expenditure (TDEE), the number that actually determines whether you gain or lose weight.
This calculator estimates BMR using one of three well-established equations, which you can select under Settings. By default it uses the Mifflin-St Jeor equation, the formula most recommended by dietitians today. After computing your BMR, the calculator multiplies it by standard activity factors to show how many calories you would need per day depending on how active you are.
Published in 1990, the Mifflin-St Jeor equation is considered the most accurate general-purpose BMR formula for the modern population:
Men: BMR = 10W + 6.25H − 5A + 5
Women: BMR = 10W + 6.25H − 5A − 161
where W is body weight in kilograms, H is height in centimeters, and A is age in years.
The original Harris-Benedict equation dates back to 1919 and was revised by Roza and Shizgal in 1984 for improved accuracy. It was the most widely used BMR formula for decades:
Men: BMR = 13.397W + 4.799H − 5.677A + 88.362
Women: BMR = 9.247W + 3.098H − 4.330A + 447.593
It tends to produce results very close to Mifflin-St Jeor for most people, usually within a few percent.
The Katch-McArdle formula is different because it is based on lean body mass rather than total weight, which means it accounts for body composition:
BMR = 370 + 21.6 × LBM
where LBM (lean body mass) = W × (1 − body fat % / 100)
Because muscle is more metabolically active than fat, the Katch-McArdle formula can be the most accurate option for lean, muscular individuals who know their body fat percentage. If you do not know your body fat, use Mifflin-St Jeor instead.
BMR and Resting Metabolic Rate (RMR) are often used interchangeably, but they are measured slightly differently. BMR is measured under very restrictive laboratory conditions - after a full night's sleep, following a 12-hour fast, while fully rested and awake in a dark, temperature-controlled room. RMR is measured under less strict conditions and therefore tends to be slightly higher (often by about 10%) because it can include a small amount of digestion and movement. In everyday use, the two terms are close enough that the BMR figure from this calculator serves as a practical estimate of your resting energy needs.
Your BMR alone is not how many calories you should eat - it is the calories you would burn doing nothing. To estimate the calories you actually need, BMR is multiplied by an activity factor that reflects your lifestyle. The result is your Total Daily Energy Expenditure (TDEE). This calculator shows the full table automatically:
To lose weight, eat fewer calories than your TDEE; to gain weight, eat more. A deficit or surplus of about 500 calories per day corresponds to roughly one pound of weight change per week.
Several variables influence how high or low your basal metabolic rate is:
While much of your BMR is determined by factors outside your control, a few strategies can raise it modestly over time:
Keep expectations realistic: these changes produce gradual, modest improvements rather than dramatic overnight shifts.
In a clinical setting, BMR is measured through a process called indirect calorimetry, which analyzes the oxygen you consume and the carbon dioxide you produce while at complete rest. This is the gold standard, but it requires specialized equipment and strict conditions. For everyday purposes, the equations used by this calculator provide a reliable estimate without any lab visit. Keep in mind that any formula-based estimate can differ from your true BMR by around 10% because of individual differences in genetics, body composition, and hormones - so treat the number as a well-grounded starting point and adjust based on real-world results.
There is no single "normal" value because BMR depends on your age, sex, height, and weight. As a rough guide, many adult women have a BMR in the range of about 1,200-1,500 calories per day and many adult men around 1,500-1,900, but yours may fall outside these ranges and still be perfectly healthy. Use your calculated figure rather than a generic average.
No. Your BMR is the energy you burn at complete rest, so eating only that amount while living a normal, active life would create a large calorie deficit. To find your actual needs, use your TDEE (BMR multiplied by an activity factor), shown in the table above.
For most people, the Mifflin-St Jeor equation is the most accurate and is the recommended default. If you are lean and know your body fat percentage, the Katch-McArdle formula may be more precise because it accounts for body composition.
BMR tends to fall with age primarily because people lose muscle mass over time, and muscle burns more energy than fat. Staying active and doing resistance training can help slow this decline.
Your BMR is relatively stable, but it can shift gradually with changes in weight, muscle mass, age, and hormones, and temporarily with factors like illness, fever, or extreme dieting. Recalculate whenever your weight changes noticeably.
No. All calculations run entirely in your browser, and nothing you enter is uploaded or saved to any server, so your data stays private.
This BMR Calculator is provided for educational and general informational purposes and is not medical advice. Estimated values are based on population formulas and can vary from individual results. Consult a doctor or registered dietitian before making significant changes to your diet or exercise routine.