How the TDEE calculator works
The equation
Mifflin-St Jeor: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + (5 for men, −161 for women). It is the most accurate widely-validated RMR equation for healthy adults — and still carries roughly ±10% individual error. TDEE = BMR × activity multiplier, where the multiplier bundles everything beyond resting: movement, training, digestion (~10% of intake), and fidgeting.
Where the error lives
Not in the formula — in the activity multiplier. Human activity varies enormously inside each "level," and people are systematically optimistic about theirs. Two honest corrections: pick the level that matches your average week including weekends, and if you are between levels, choose lower. A sedentary job with three gym sessions is "light," not "moderate."
Using the number
- Maintain: eat at TDEE and watch scale trend for 2–3 weeks.
- Cut: TDEE − 15–20% (usually 400–600 kcal) — our macro split calculator applies this.
- Bulk: TDEE + 10% for lean gains; +20% only for underweight athletes.
The scale is the arbiter: if weight trend disagrees with the calculation for three weeks, the calculation is wrong for you — adjust by 100–200 kcal and re-test. Formulas start the process; measurement finishes it.