BMR & Daily Calorie Needs Calculator
Find your Basal Metabolic Rate and total daily calorie needs using the Mifflin-St Jeor equation. Enter your weight, height, age, and activity level to get a personalized calorie target for weight loss, maintenance, or gain.
About this calculator
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to sustain basic functions like breathing and circulation. This calculator uses the Mifflin-St Jeor equation, widely regarded as the most accurate BMR formula for most adults. For males: BMR = 88.362 + (13.397 × weight_kg) + (4.799 × height_cm) − (5.677 × age). For females: BMR = 447.593 + (9.247 × weight_kg) + (3.098 × height_cm) − (4.330 × age). To find your Total Daily Energy Expenditure (TDEE), the BMR is multiplied by an activity factor ranging from 1.2 (sedentary) to 1.9 (very active). TDEE represents the calories you need each day to maintain your current weight — eat below it to lose weight, above it to gain.
How to use
Suppose you are a 30-year-old male weighing 80 kg and standing 175 cm tall with a moderately active lifestyle (activity factor 1.55). Step 1 — Calculate BMR: 88.362 + (13.397 × 80) + (4.799 × 175) − (5.677 × 30) = 88.362 + 1071.76 + 839.825 − 170.31 = 1,829.64 kcal/day. Step 2 — Multiply by activity factor: 1,829.64 × 1.55 = 2,835.9 kcal/day. This means you need roughly 2,836 calories per day to maintain your weight at that activity level.
Frequently asked questions
What is the difference between BMR and TDEE, and which should I use for dieting?
BMR is the calories your body needs at complete rest — essentially the energy to keep your organs functioning. TDEE (Total Daily Energy Expenditure) adds the calories burned through daily movement and exercise on top of BMR. For dieting purposes, TDEE is the number you should use, since it reflects your real-world calorie burn. Eating below your TDEE creates a deficit that leads to weight loss, while eating at TDEE maintains your current weight.
Why does the Mifflin-St Jeor equation give different values for males and females?
Biological differences in body composition mean males typically have more lean muscle mass relative to fat compared to females of the same weight and height, and muscle tissue burns more calories at rest. The Mifflin-St Jeor equation accounts for this by using different baseline constants and coefficients for each sex. Research has shown this equation is more accurate than older formulas like Harris-Benedict for predicting resting metabolic rate in modern populations. Using the wrong gender input will noticeably skew your calorie estimate.
How accurate is the BMR calculator and what factors can affect my actual metabolic rate?
The Mifflin-St Jeor equation is accurate within roughly 10% for most healthy adults, making it the most reliable non-laboratory estimate available. However, factors like muscle-to-fat ratio, hormonal conditions (e.g., thyroid disorders), medications, and genetics can push your true BMR above or below the prediction. Athletes with high muscle mass will often have a higher actual BMR than the formula suggests, while very sedentary individuals may have a lower one. For the most precise measurement, a clinical resting metabolic rate test using indirect calorimetry is the gold standard.