Calculate your Basal Metabolic Rate using Harris-Benedict, Mifflin-St Jeor, Katch-McArdle, and Cunningham equations. Estimate TDEE for weight goals.
Your Basal Metabolic Rate (BMR) is the number of calories your body needs to perform essential life-sustaining functions — breathing, circulating blood, regulating body temperature, producing cells, and maintaining organ function — while completely at rest. BMR typically accounts for 60–75% of your total daily energy expenditure (TDEE), which is why it is often used as a starting estimate for broader calorie planning.
This calculator compares four established equations. Mifflin-St Jeor is commonly used as the default estimate for the general population. Harris-Benedict is older and still widely referenced. Katch-McArdle and Cunningham use lean body mass, which can be useful when body fat percentage is known and body composition differs meaningfully from the average assumed by weight-based formulas.
Once your BMR is estimated, the page applies an activity factor (1.2–1.9) to estimate TDEE — the total calories burned each day including exercise and general movement. From there, you can sketch out rough calorie ranges for maintenance, fat loss, or weight gain, then refine them from real-world results.
Knowing your BMR helps turn a vague calorie goal into a more structured estimate. Whether your goal is maintenance, fat loss, or weight gain, comparing several equations side by side gives you a starting range that can then be adjusted from your weight trend, appetite, and training response.
Mifflin-St Jeor: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age − 161 (female) or + 5 (male). Harris-Benedict (revised): Male = 88.362 + 13.397w + 4.799h − 5.677a; Female = 447.593 + 9.247w + 3.098h − 4.330a. Katch-McArdle: BMR = 370 + 21.6 × lean body mass(kg). Cunningham: BMR = 500 + 22 × lean body mass(kg). TDEE = BMR × Activity Factor.
Result: Mifflin-St Jeor BMR: 1,780 kcal/day; TDEE: 2,759 kcal/day
For a 30-year-old male, 80 kg, 180 cm: 10×80 + 6.25×180 − 5×30 + 5 = 1,780 kcal/day. Multiplied by activity factor 1.55 gives a TDEE of approximately 2,759 kcal/day. For moderate weight loss, target about 2,259 kcal/day (−500 deficit).
The original Harris-Benedict equations were published in 1919 and later revised in 1984. Mifflin-St Jeor was developed in 1990 and is widely used in modern nutrition calculators. Katch-McArdle and Cunningham were built around lean body mass, which is why they are often more useful when body-composition data is available.
BMR equations describe average resting energy use from a limited set of inputs. They do not capture every factor that can influence energy expenditure, such as medication use, illness, hormones, spontaneous movement, or major differences in lean mass. That is why calculator results work best as starting estimates rather than fixed calorie prescriptions.
TDEE includes BMR plus the thermic effect of food, exercise activity, and non-exercise activity. Non-exercise activity is often the most variable part, which is why two people with the same BMR can still maintain weight on noticeably different calorie intakes.
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This page calculates resting energy expenditure with up to four common equations: Mifflin-St Jeor, revised Harris-Benedict, Katch-McArdle, and Cunningham when body fat is available. It then multiplies those results by the selected activity factor to show rough daily-energy ranges. These are starting estimates for planning, not direct metabolic measurements.
BMR is measured under strict resting conditions (12-hour fast, complete rest, thermoneutral environment). RMR (Resting Metabolic Rate) is measured under less strict conditions and is typically 10–20% higher than BMR. Most online calculators estimate RMR but label it BMR.
Mifflin-St Jeor is commonly used as a general-purpose starting estimate for adults. If you know your body fat percentage, Katch-McArdle may fit some leaner or more muscular individuals better because it uses lean body mass instead of total weight.
Yes. BMR decreases approximately 1–2% per decade after age 20, primarily due to loss of muscle mass (sarcopenia). Resistance training can slow this decline by preserving lean tissue.
Muscle tissue is metabolically active and burns about 6 kcal/lb/day at rest, compared to fat tissue which burns about 2 kcal/lb. More muscle mass = higher BMR, which is why the Katch-McArdle formula using lean body mass can be more accurate for muscular individuals.
Eating far below estimated energy needs for extended periods can increase the risk of fatigue, muscle loss, nutrient shortfalls, and other problems. Very low-calorie plans are better reviewed with a qualified clinician or dietitian than set from a calculator alone.
Activity multipliers are population averages and can vary by ±10–20% between individuals. Factors like NEAT (Non-Exercise Activity Thermogenesis), genetics, and metabolic adaptation affect actual TDEE. Use the calculated TDEE as a starting point, then adjust based on real-world weight trends over 2–4 weeks.