TDEE — total daily energy expenditure — is the total number of calories your body spends in a 24-hour day. It includes what you would burn lying still, the energy it costs to digest what you eat, the calories spent in training, and everything in between: walking to the car, standing, fidgeting, carrying shopping. When a calorie calculator says "maintain at 2,837 kcal", TDEE is the number it is talking about.
The FAO/WHO/UNU expert report that most reference values descend from defines it plainly as the energy spent, on average, in a 24-hour period1. Everything else in this article is about what that total is made of and how a calculator guesses it.
What TDEE is made of
Four things spend energy in a day. Nutrition textbooks usually give them these names:
| Component | What it is | Typical share of TDEE |
|---|---|---|
| BMR (basal metabolic rate) | The cost of being alive at complete rest — heart, lungs, brain, cell turnover | 45–70% (often quoted as ~70% for a sedentary adult) |
| TEF (thermic effect of food) | The energy it takes to digest, absorb and store what you eat | ≈ 10% of BMR over a day; roughly 10% of intake |
| EAT (exercise activity thermogenesis) | Deliberate training — lifting, running, sport | ~5% for most people, far more for athletes |
| NEAT (non-exercise activity thermogenesis) | All other movement — walking, standing, housework, fidgeting | ~15%, and the most variable slice |
The 45–70% band for BMR and the "about 10 percent of the BMR" figure for the metabolic response to food are the expert-consultation figures1; the same report calls physical activity the most variable component and, after BMR, the second largest. The ~70 / 10 / 5 / 15 split you see in most explainers (including our figure above) is a rounded textbook illustration for a lightly active adult, not a measurement of anyone in particular.
In plain terms: most of your daily energy goes to simply existing, a tenth goes to processing food, and the rest is movement — of which exercise is usually the smaller part.
BMR, TEF, EAT and NEAT in numbers
Put the shares against a real total and the sizes become concrete. Take the worked example we use across these articles — a 30-year-old man, 180 cm, 85 kg, training four to six times a week — whose calculator TDEE comes out at 2,837 kcal (the arithmetic is in the next section).
| Component | Share used | kcal/day in the example |
|---|---|---|
| BMR | equation value | 1,830 |
| TEF | ≈ 10% of BMR | ≈ 183 |
| EAT + NEAT | the remainder | ≈ 824 |
| Total | — | 2,837 |
Two things stand out. First, BMR is 64% of this person's total, inside the 45–70% band. Second, all of the movement in a week with four to six training sessions adds up to roughly 824 kcal a day — and the training sessions are only part of that. The other part is NEAT, which is why two people with identical gym habits and identical bodies can differ by several hundred kcal a day. This is arithmetic on the calculator's own output, not a measurement.
How a calculator estimates it
No calculator measures anything. It estimates BMR from an equation, then multiplies by a factor that stands in for TEF, EAT and NEAT together. Our calorie calculator uses the Mifflin-St Jeor equation, which was fitted to 498 healthy adults measured by indirect calorimetry2:
- Men:
BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 - Women:
BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161
The multiplier is built from two questions rather than one: how many training sessions a week (0 → 1.2, 1–3 → 1.375, 4–6 → 1.55, 7+ → 1.725) and how much you move outside training (sedentary −0.05, moderate 0, very active +0.10). Added together they span 1.15 to 1.825. The expert report calls this ratio the physical activity level, or PAL — TEE expressed as a multiple of BMR1.
TDEE = round(BMR × (exercise base + NEAT adjustment))
Why the estimate can be off by a few hundred kcal
Both halves of the estimate are population averages. Mifflin-St Jeor explains about 71% of the variation in measured resting expenditure across its sample2; the remaining 29% is individual. In practice that means a typical miss of 100–200 kcal on BMR alone, with individual misses of 400–500 kcal not unusual. Then the multiplier buckets "4–6 sessions a week" into one number, whether those sessions are 30-minute machine circuits or two-hour squat days.
Neither error is a flaw in the maths. A formula can only know what you typed. What it cannot know is how much you fidget, how efficiently you move, or how your body responds to a deficit — and those are exactly the things that decide your real TDEE. The honest way to use a calculator is as a first guess to be corrected by two weeks of logged intake and trend weight, which is what MacroDiet's expenditure estimate does (see how apps estimate energy expenditure).
Worked example (85 kg, 4–6 sessions a week)
Male, 30 years, 180 cm, 85 kg, four to six sessions a week, moderate NEAT:
BMR = 10×85 + 6.25×180 − 5×30 + 5 = 850 + 1,125 − 150 + 5 = 1,830multiplier = 1.55 + 0 = 1.55TDEE = round(1,830 × 1.55) = 2,837 kcal/day
Change only the NEAT answer and the total moves: sedentary outside the gym gives 1,830 × 1.50 = 2,745; very active gives 1,830 × 1.65 = 3,020. A 275 kcal swing from one question — which is the point of asking it separately.
This is arithmetic, not a trial result. The calculator reproduces these numbers exactly; whether they match your body is what the next two weeks of tracking will tell you.
The short version
TDEE is everything you spend in a day: resting metabolism (the biggest slice, 45–70%), digestion (about a tenth), training, and the large, variable pile of ordinary movement called NEAT. A calculator estimates it as BMR × multiplier; ours gives 2,837 kcal for an 85 kg man training four to six times a week. Expect the estimate to be a couple of hundred kcal off in either direction, and let real intake and weight data refine it. Educational overview only — not medical advice.