The four things TDEE is made of
TDEE is usually broken into four parts, and they are wildly unequal in size:
That last row is the one people underestimate. Non-exercise activity thermogenesis varies enormously between individuals — a restless person can burn several hundred more calories a day than a still one of identical size, without either of them exercising. It is also why the activity dropdown, not your gym schedule, is the biggest lever on the result above.
How the multiplier works
The calculator estimates your basal rate with Mifflin-St Jeor, then multiplies:
- Sedentary× 1.2desk job, no exercise
- Lightly active× 1.3751–3 days a week
- Moderately active× 1.553–5 days a week
- Very active× 1.7256–7 days a week
- Extra active× 1.9physical job or two-a-days
TDEE = BMR × multiplier
What to do with the number
TDEE is not a target on its own — it is the reference point. Eat at it to maintain. Eat below it to lose, above it to gain. Everything the other calculators do is arithmetic performed on this one figure, which is why it is worth getting roughly right before anything else.
The honest way to use it: take the estimate, eat at it for two to three weeks, and weigh yourself often enough to see a trend rather than noise. If your weight is stable, the estimate was good. If it drifts, your real TDEE is the estimate plus or minus about 500 calories, and now you know which direction. After a month of that, your own data is a better predictor than any equation.
From here you can size your calorie deficit against this number, or see what you burn at rest to understand how much of it is simply being alive.
Sources
Mifflin MD, St Jeor ST, et al. “A new predictive equation for resting energy expenditure in healthy individuals.” Am J Clin Nutr, 1990.
Levine JA. “Non-exercise activity thermogenesis (NEAT).” Best Pract Res Clin Endocrinol Metab, 2002 — on the size of the NEAT range between individuals.
Frankenfield D, et al. “Comparison of predictive equations for resting metabolic rate in healthy nonobese and obese adults.” J Am Diet Assoc, 2005 — why Mifflin-St Jeor is the usual default.
