TDEE Formula
Every TDEE formula works the same way: estimate resting metabolism (BMR) from your body statistics, then multiply by an activity factor. This page gives you the actual equations, the multiplier table, and two fully worked examples, so you can check any calculator's math by hand — including ours.
Step 1: The BMR Equations
Mifflin-St Jeor (used by our calculator, and generally the most accurate for the general population in validation studies). Weight in kg, height in cm, age in years:
- Men: BMR = 10 × weight + 6.25 × height − 5 × age + 5
- Women: BMR = 10 × weight + 6.25 × height − 5 × age − 161
Revised Harris-Benedict (an older alternative you will still see in many apps):
- Men: BMR = 13.397 × weight + 4.799 × height − 5.677 × age + 88.362
- Women: BMR = 9.247 × weight + 3.098 × height − 4.330 × age + 447.593
Katch-McArdle (uses lean body mass instead of sex, so it needs a body-fat estimate — you can get one from the Navy body fat calculator):
- BMR = 370 + 21.6 × lean body mass (kg)
Step 2: The Activity Multipliers
TDEE = BMR × the factor that matches your normal week, not your best week:
| Activity level | Description | Multiplier |
|---|---|---|
| Sedentary | Little or no exercise, desk job | 1.2 |
| Lightly active | Light exercise 1–3 days/week | 1.375 |
| Moderately active | Moderate exercise 3–5 days/week | 1.55 |
| Very active | Hard exercise 6–7 days/week | 1.725 |
| Super active | Very hard exercise plus a physical job | 1.9 |
When in doubt, pick the lower bracket. Overstating activity is the single most common reason a calculated TDEE overshoots reality, and it silently erases part of your intended deficit.
Worked Example 1: Male
30-year-old man, 80 kg, 180 cm, moderate exercise 3–5 days/week:
- BMR = 10 × 80 + 6.25 × 180 − 5 × 30 + 5 = 800 + 1,125 − 150 + 5 = 1,780 kcal
- TDEE = 1,780 × 1.55 ≈ 2,759 kcal
- Cutting target ≈ 2,259 kcal (TDEE − 500); lean-gain target ≈ 3,259 kcal (TDEE + 500)
Worked Example 2: Female
28-year-old woman, 62 kg, 165 cm, light exercise 1–3 days/week:
- BMR = 10 × 62 + 6.25 × 165 − 5 × 28 − 161 = 620 + 1,031 − 140 − 161 = 1,350 kcal
- TDEE = 1,350 × 1.375 ≈ 1,857 kcal
- A moderate cut would sit around 1,500–1,600 kcal rather than the full −500, which would be aggressive at her size.
Which Formula Should You Use?
- Default: Mifflin-St Jeor. Best-validated for the general population; it is what our TDEE calculator runs.
- Know your body fat and carry above-average muscle? Katch-McArdle can be more representative, because it works from lean mass directly.
- Harris-Benedict mainly matters for comparing against older apps; it tends to estimate slightly higher than Mifflin-St Jeor for many inputs.
Whichever equation you pick, remember the error bars: formulas are typically within about 10% for healthy adults. The formula gives the starting point; 2–3 weeks of weekly-average weight data gives the truth. The calibration loop is described in maintenance calories, and applying the result to a cut is covered in TDEE for weight loss.
Frequently Asked Questions
Why does the women's Mifflin-St Jeor equation subtract 161?
The constants encode average body-composition differences between sexes at the same height and weight; women
typically carry a higher fat-to-lean ratio, and lean tissue drives resting burn.
Can I just multiply body weight by a number, like 15 kcal per pound?
Quick per-pound rules land in the right neighborhood for average builds but ignore age and height entirely. The
full formula costs nothing extra when a calculator does it for you.
Do I need to redo the math as I lose weight?
Yes — TDEE falls as weight falls. Recalculate every 4 to 8 weeks or after roughly every 5 kg of change.