What this tool does
TDEE is an estimate of calories that would hold today’s body weight if intake and activity stay similar. The page also shows a milder and a standard fat-loss band and a lean-to-moderate surplus band so you can see the neighborhood without opening three tools.
How it works
BMR comes from Mifflin-St Jeor. Activity multiplies it: 1.2 desk-and-little-training up to 1.9 physical job or two-a-days. Pick the line that sounds like a normal week, including walks. Harris-Benedict is not used for the headline TDEE here.
Formula and methodology
TDEE = Mifflin-St Jeor BMR × activity factor (1.2, 1.375, 1.55, 1.725, 1.9). Multipliers are population conveniences from older factorial systems. They do not measure fidgeting, desk fidget, or a brutal job plus gym.
How to interpret the result
If two weeks of eating near this number and a stable weekly average agree, you have a working maintenance. If weight drops, the estimate was high or you under-logged. If weight climbs, the reverse. Confirm before you cut or add a large slice.
Example
The same 80 kg, 180 cm, 30-year-old man at moderate (1.55) lands near 2,760 kcal TDEE. Sedentary would be about 2,140 kcal; active about 3,070 kcal. Mis-clicking activity by one rung is a 300–400 kcal error — larger than many “diets.”
Common mistakes
- Counting both a physical job and “very active” gym days when the job already filled the multiplier.
- Using TDEE as a license to ignore protein.
- Copying a partner’s TDEE because you train together.
- Updating TDEE from a single heavy restaurant day.
When this estimate may be off
- You recently lost a lot of weight and expenditure has adapted downward.
- Injury or a desk week replaced the activity you typed.
- Height or weight is off by enough to move BMR tens of calories, then the multiplier amplifies it.
- You are still growing, pregnant, or in a clinical metabolic setting this formula was not built for.