TDEE stands for total daily energy expenditure. It is the total energy a person uses in a day — everything from staying alive at rest to training, digesting food and walking around the house. It is the number a calorie target is set against.
Eat below TDEE and a client loses weight; eat above it and they gain. That makes it the most useful number in nutrition coaching, and the one most often treated as fact when it is an estimate.
What TDEE is made of
Four components, and they are not close to equal in size.
| Component | What it covers | Rough share |
|---|---|---|
| Basal metabolic rate (BMR) | Energy used at complete rest — organs, breathing, cell turnover, keeping body temperature up | 60–70% |
| Non-exercise activity (NEAT) | Everything that is not deliberate training: walking, standing, housework, fidgeting, occupation | 15–30% |
| Exercise activity (EAT) | Sessions the client actually trains | 5–10% for most clients, more for endurance athletes |
| Thermic effect of food (TEF) | Energy used digesting, absorbing and storing what they eat | About 10% |
BMR is the biggest slice and the one you have least influence over. It scales with body size and lean mass, which is why a 95kg client and a 60kg client on the same calorie target end up in very different places.
The share that moves most is NEAT. Between two clients of similar size it can differ by more than 1,000 calories a day — a tradesperson on their feet against a desk worker. It also drops during a diet, without the client deciding to move less, which is why a deficit that worked in week three stops working in week ten.
Training is usually the smallest slice, and clients consistently overestimate it. Four gym sessions a week might be 250–400 calories a session, not the 700 the cardio machine reported.
TEF depends on what is eaten rather than how much someone moves. Protein costs roughly 20–30% of its own energy to process, carbohydrate around 5–10%, fat close to nothing — a minor reason among better ones to push protein up when you set macros.
Why the calculator number is an estimate
A TDEE calculator does two things. First it predicts BMR from height, weight, age and sex using an equation — Mifflin-St Jeor is the common one, Katch-McArdle if you have a body fat figure. Then it multiplies that by an activity factor, usually between 1.2 and 1.9, chosen from a dropdown.
Both steps carry error. The prediction equations land within about 10% for most people, which on a 1,600 calorie BMR is a 160 calorie band before you have multiplied anything. The activity multiplier is worse: the buckets are coarse and one step up the list is often 300 calories or more. Asking a client whether they are "moderately active" or "very active" is asking them to guess.
So treat the output as a range. If the calculator says 2,400, the honest reading is "somewhere between 2,100 and 2,700" — a starting target, not a finding.
Measured intake beats a predicted number
Two weeks of logged food and body weight tells you more than any equation. If a client averages 2,300 calories a day over 14 days and their weight is flat, their TDEE is about 2,300 — measured, not predicted. If they lost half a kilo across those two weeks, they were running roughly a 275 calorie daily deficit, so maintenance is nearer 2,575. The full method, including how to turn that into macros, is in how to calculate TDEE and macros for clients.
This only works if the logging is consistent. Under-reporting is normal rather than deceitful — cooking oil, milk in coffee, the bites while making dinner — and a client who under-reports the same way every day still gives you a usable number. One whose logging falls apart on weekends does not.
In Fitsly a client's food log week shows their average daily calories against their goal and how many of the seven days they actually logged — the second number you need before you trust the first.
TDEE moves, so the target has to
Maintenance is not a fixed property of a client. It falls as they lose weight, because there is less body to carry and less tissue to fuel, and falls further because NEAT and often training quality drop in a deficit. It rises when they gain weight, add volume, or change to a job that keeps them moving.
None of it is visible in the moment when you coach asynchronously. It shows up as a stall in the numbers a client sends you, which is the argument for a regular check-in that captures weight and intake together rather than one without the other.
One limit worth naming. All of this is general information for healthy adults. A client with a medical condition, a medication that affects appetite or weight, or a history of disordered eating belongs with an accredited dietitian or their doctor, so refer rather than estimate.
