Formula: BMR, then activity multiplier
TDEE is built in two steps. First the Mifflin–St Jeor equation estimates basal metabolic rate (BMR), the energy your body uses at complete rest:
BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + s
s = +5 for male, −161 for femaleImperial inputs are converted first (pounds × 0.453592, inches × 2.54). Then BMR is multiplied by an activity factor to give TDEE:
| Activity level | Factor |
|---|---|
| Sedentary | 1.2 |
| Light (1–3 days/week) | 1.375 |
| Moderate (3–5 days/week) | 1.55 |
| Active (6–7 days/week) | 1.725 |
| Very active (hard daily or physical job) | 1.9 |
Worked example
A 30-year-old man, 175 cm and 75 kg, exercising 3–5 days a week. BMR = 750 + 1,093.75 − 150 + 5 = 1,698.75 kcal. TDEE = 1,698.75 × 1.55 = 2,633 kcal. The page then shows 2,133 kcal (−500) and 3,133 kcal (+500) as lose and gain targets.
The macro split
This is the distinguishing part of this page. The calorie total is divided into a fixed 30% protein, 40% carbohydrate and 30% fat split at your maintenance level, using 4 kcal per gram for protein and carbohydrate and 9 kcal per gram for fat. For the example that is 197 g protein, 263 g carbs and 88 g fat. The split cannot be adjusted on the page, so treat it as a balanced starting point, not a prescription for any particular diet.
Where the estimate goes wrong
- Overstating activity. Most people pick a level higher than their real week. If your weight does not move as predicted over two to three weeks, drop one level.
- Population averages. The equation was fitted to groups of adults. Individual metabolisms commonly differ by a few hundred kcal a day, and very muscular or very lean bodies fall outside its typical error.
- Low targets. Nothing is clamped, but if the lose-weight figure drops below about 1,200 kcal (women) or 1,500 kcal (men), the commonly cited minimums for unsupervised dieting, a warning appears under the targets. It is general guidance, not medical advice.
- Static output. TDEE falls as you lose weight, so a deficit that works in week one is smaller by month three. Recalculate with your current weight.
- Not for everyone. The figures are general estimates, not medical advice, and are not designed for children, pregnancy or medical conditions.
If you only need the lose/gain targets and a protein figure, the calorie calculator shows milder and standard steps. For body-size context see the BMI calculator and the guide on BMI and daily calorie needs.