BMR & TDEE Calculator
Calculate your Basal Metabolic Rate (BMR) and Total Daily Energy Expenditure (TDEE) using the Mifflin–St Jeor equation. Essential for setting accurate calorie targets when losing, gaining, or maintaining weight.
About this calculator
Basal Metabolic Rate (BMR) is the number of calories your body burns at complete rest to sustain vital functions. This calculator uses the Mifflin–St Jeor equation, the most validated formula for general populations. 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). TDEE is then calculated by multiplying BMR by an activity factor — typically 1.2 (sedentary) through 1.725 (very active) or higher for athletes. TDEE represents your actual daily calorie requirement inclusive of all movement. Eating below TDEE creates a deficit for fat loss; eating above creates a surplus for muscle gain.
How to use
Example: 30-year-old woman, 65 kg, 165 cm, moderately active (activity factor = 1.55). Step 1 — BMR: 447.593 + (9.247 × 65) + (3.098 × 165) − (4.330 × 30) = 447.593 + 601.055 + 511.170 − 129.900 = 1 429.9 kcal/day. Step 2 — TDEE: 1 429.9 × 1.55 = 2 216 kcal/day. This woman needs approximately 2 216 kcal/day to maintain her current weight. To lose ~0.5 kg/week she would target roughly 1 716 kcal/day (a 500 kcal deficit).
Frequently asked questions
What is the difference between BMR and TDEE, and which one should I use for my diet?
BMR (Basal Metabolic Rate) is the calories your body needs at complete rest — essentially the energy cost of staying alive with no movement whatsoever. TDEE (Total Daily Energy Expenditure) builds on BMR by accounting for all physical activity throughout the day. For practical diet planning, TDEE is the number you should use, since it represents what you actually burn. Eating at your TDEE maintains weight, eating below it creates a deficit for fat loss, and eating above it promotes muscle and weight gain.
How accurate is the Mifflin–St Jeor equation for calculating calorie needs?
The Mifflin–St Jeor equation is considered the most accurate predictive equation for resting metabolic rate in the general population, outperforming the older Harris–Benedict formula in multiple validation studies. On average it predicts BMR within 10% for most adults, though accuracy decreases at the extremes of body composition — very lean, highly muscular individuals may have a higher BMR than predicted, while those with very high body fat percentages may have a lower one. The activity multiplier introduces additional variability, as most people tend to overestimate their activity level. For precise results, indirect calorimetry testing is the gold standard.
How does age affect your BMR and daily calorie requirements?
BMR declines with age primarily because of a gradual loss of lean muscle mass, a process called sarcopenia that typically begins in the mid-30s. Muscle tissue is metabolically expensive — it burns roughly 3 times more calories at rest than fat tissue. The Mifflin–St Jeor equation reflects this by subtracting approximately 5–6 calories per year of age. A 50-year-old with the same weight and height as a 25-year-old will have a BMR roughly 125–150 kcal/day lower. Resistance training is the most effective strategy for slowing age-related BMR decline by preserving muscle mass.