The definition
TDEE — Total Daily Energy Expenditure — is the total number of calories your body burns in a day. Eat that many calories and your weight stays stable. Eat fewer and you lose; eat more and you gain. Everything else is detail.
The four parts of your daily burn
- BMR (60–70%) — your Basal Metabolic Rate: calories burned at complete rest just to stay alive.
- Activity (NEAT + exercise, 15–30%) — everything you do, from workouts to fidgeting and walking.
- Thermic effect of food (~10%) — the energy used to digest what you eat (protein costs the most).
Add them up and you get your TDEE. Our TDEE calculator estimates it using the Mifflin-St Jeor equation and your activity level.
How to use your TDEE
- Lose fat: eat about 300–500 calories below TDEE (a 10–20% deficit).
- Maintain: eat around TDEE.
- Build muscle: eat about 200–400 above TDEE, with strength training.
Why it's an estimate
TDEE formulas are starting points — your true burn varies with muscle mass, genetics, and daily movement, and it changes as your weight changes (a lighter body burns less). Use the calculated number for 2–3 weeks, watch your weight trend, and adjust. The scale is the real feedback; the formula just gets you close.
The takeaway
You don't need to obsess over a perfect number. Know your rough TDEE, pick a goal, set calories accordingly, then let real-world results fine-tune it.
NEAT: the component nobody accounts for
Non-exercise activity thermogenesis covers everything you burn that is neither sleeping, eating, nor deliberate exercise — walking to the kitchen, standing, fidgeting, gesturing while talking, shifting in your chair.
It is the most variable component of daily expenditure by a wide margin. Two people of identical size and exercise habits can differ by several hundred calories a day purely through unconscious movement, which explains a great deal of the mystery around why some people seem to eat freely without gaining weight.
What makes NEAT genuinely important for anyone dieting is that it is not fixed. When you eat less, NEAT tends to fall — you move less, sit more, take the lift, fidget less — and it happens without any conscious decision. This is a real, measurable contributor to the plateau people encounter partway through a fat-loss phase, and it operates independently of any change in resting metabolism.
The practical response is to track something objective. A daily step count is a crude but effective proxy: if your steps have quietly dropped from 9,000 to 5,000 over six weeks of dieting, you have found several hundred calories of your missing deficit.
Why your TDEE is a moving target
The most common mistake with TDEE is treating it as a fixed personal constant. It is not — it falls as you lose weight, for three separate reasons that compound.
A smaller body has less tissue to maintain, so resting metabolism drops. Moving a lighter body costs less energy per step, so the same walk burns fewer calories. And, as above, NEAT tends to decline during restriction.
Modelling work published in the Lancet by Kevin Hall and colleagues quantifies this properly, and its conclusion is worth internalising: a sustained change in calorie intake does not produce indefinite linear weight change. It moves you toward a new steady weight, approached gradually over roughly a year. The old rule that 3,500 calories equals a pound therefore overpredicts increasingly as you go.
Practically: recalculate every 5 to 10 kilograms lost, or whenever progress genuinely stalls for three weeks or more. The plateau most people interpret as a broken metabolism is usually just the arithmetic arriving.
Common mistakes when using TDEE
Three errors account for most of the frustration people have with calorie targets.
Overstating activity. This is the big one. The activity multiplier swings the result by hundreds of calories, and almost everyone rounds up. Three gym sessions a week alongside a desk job is "light", not "active". If you are between two levels, pick the lower one — it is far easier to add food when you are losing faster than planned than to explain away a month of nothing.
Double-counting exercise. If your multiplier already includes training, eating back the calories your watch says you burned counts the same energy twice. Pick one method and stick to it.
Treating the estimate as measured. The equation is a prediction with roughly a 10% margin. The scale over two to three weeks is the actual measurement, and when the two disagree, the scale is right.