Adaptive TDEE Calculator
Every formula on this site predicts your TDEE from your body size. This page does the opposite: it takes what you actually ate and what your weight actually did, and works backwards to the number your body is really running at.
How the arithmetic works
A kilogram of body mass change is treated as roughly 7700 kcal. If your weight fell over the period, you ate that much under your real TDEE; if it rose, you ate over it.
Real TDEE = average daily intake - (weight change kg x 7700 / days)Step 1 - Weight change
-0.6 kg (lost)Step 2 - Convert to a daily surplus or deficit
-0.6 x 7700 / 21 = -220 kcal/dayStep 3 - Add it back to intake
2400 - (-220) = 2620 kcal/dayYour measured TDEE
2620 kcal per day
Why formulas drift
Predictive equations assume an average person and an activity factor you picked yourself. Metabolism varies between people of identical size, and the activity multiplier is the biggest guess in the whole calculation. Two weeks of your own data beats anyone's equation.
Read this before trusting the number
Track at least 14 days, ideally 21. Shorter windows are dominated by water weight, glycogen and gut contents rather than fat. The result is also only as good as your intake logging, which most people underestimate.
Starting out and have no data yet? Begin with the Mifflin-St Jeor calculator.