BMR & TDEE Calculator
Estimates your Basal Metabolic Rate (calories burned at rest) and Total Daily Energy Expenditure using the Mifflin-St Jeor equation. Use it to set a science-backed calorie target for weight loss, maintenance, or muscle gain.
About this calculator
Your Basal Metabolic Rate (BMR) is the number of calories your body burns just to stay alive — breathing, circulating blood, and maintaining organ function. This calculator uses the Mifflin-St Jeor equation, the most widely validated formula for estimating BMR. For men: BMR = 88.362 + (13.397 × weight_kg) + (4.799 × height_cm) − (5.677 × age). For women: BMR = 447.593 + (9.247 × weight_kg) + (3.098 × height_cm) − (4.330 × age). Your TDEE (Total Daily Energy Expenditure) is then calculated by multiplying BMR by an activity factor — ranging from 1.2 (sedentary) to 1.9 (very active). The result tells you how many calories you must consume daily to maintain your current weight, so you can then create a deficit or surplus to meet your goals.
How to use
Suppose you are a 30-year-old male, 180 lbs (81.6 kg), 70 inches tall (177.8 cm), with a moderately active lifestyle (activity factor 1.55). Step 1 — Calculate BMR: 88.362 + (13.397 × 81.6) + (4.799 × 177.8) − (5.677 × 30) = 88.362 + 1093.2 + 853.2 − 170.3 = 1,864 calories. Step 2 — Multiply by activity factor: 1,864 × 1.55 = 2,889 calories. Your TDEE is approximately 2,889 calories/day. To lose 1 lb/week, subtract ~500 calories, targeting roughly 2,389 calories daily.
Frequently asked questions
What is the difference between BMR and TDEE for weight loss?
BMR is the number of calories your body burns at complete rest — it keeps your heart beating and lungs breathing. TDEE adds on top of BMR all the calories burned through daily movement, exercise, and digestion. For weight loss, you need to eat below your TDEE, not your BMR. Eating at or below BMR for extended periods is generally unsafe and can cause muscle loss and metabolic adaptation.
How accurate is the Mifflin-St Jeor equation for calculating BMR?
The Mifflin-St Jeor equation is considered the most accurate predictive formula for most healthy adults, with studies showing it comes within 10% of measured resting metabolic rate for roughly 80% of people. It does not account for unusually high or low body-fat percentages, so very muscular or very obese individuals may see larger deviations. For those cases, a body-composition-adjusted formula like Katch-McArdle may be more precise. Still, Mifflin-St Jeor is the gold standard recommended by most registered dietitians.
How should I choose the right activity level multiplier for my TDEE?
Activity multipliers range from 1.2 for desk jobs with no exercise up to 1.9 for hard physical labor or twice-daily training. Most people underestimate how sedentary they are and overestimate their exercise intensity, which leads to overeating. A practical approach is to start with the multiplier one step below what feels right, track your weight for two weeks, and adjust. Remember that the multiplier covers ALL movement, including non-exercise activity like walking and fidgeting, not just formal workouts.