About the TDEE Calculator
Total daily energy expenditure is everything you burn in a day: your resting metabolic rate multiplied by an activity factor.
It is the number that actually matters for eating. Maintenance is TDEE, a deficit is below it, a surplus above it. BMR on its own is only the floor.
This TDEE calculator does the arithmetic, and then does something most do not: it tells you which half of the estimate is carrying the error. Because almost everybody worries about the wrong half.
How to Use the TDEE Calculator
Enter age, sex, height and weight, then pick an activity level.
Body fat percentage is optional — supply it and the resting figure uses Katch-McArdle, which works from lean mass, instead of Mifflin-St Jeor.
Step-by-Step Example
Male, 35, 180cm, 80kg, moderately active.
Resting burn (Mifflin-St Jeor): 1,755
× 1.55 for moderately active
──────
TDEE: 2,720Realistic range: 2,448 to 2,992, because the underlying equation carries ±10% before the activity guess is even applied.
The Error Is in the Dropdown, Not the Equation
People spend real effort choosing between Mifflin-St Jeor and Harris-Benedict. Then they pick an activity level off a five-item list in about two seconds.
The effort is on the wrong one, and not by a little:
| Source of error | Effect on this example |
|---|---|
| Different BMR equation | 109 calories |
| One activity category out | 307 calories |
| Sedentary vs moderately active | 614 calories |
A single category step is nearly three times the entire disagreement between the equations. Being two out is more than five times.
Across the whole scale, sedentary to extra active spans 58% — and that percentage is the same for everyone, because it is just a ratio of the factors.
The calculator computes both gaps for your own figures and says which is dominating. It is almost always the activity guess.
What the Multiplier Actually Covers
This is why the categories are so coarse, and it is not laziness.
The factor is not "how much do you exercise". Its largest and most variable component is NEAT — non-exercise activity thermogenesis. Walking about, standing, taking stairs, fidgeting, gesturing. Everything that is not deliberate training.
Measured NEAT differs between otherwise similar people by up to around 2,000 calories a day. That is not a rounding error; it is larger than many people's entire resting burn.
The thermic effect of food — roughly 10% of what you eat, spent digesting it — is also folded into these factors.
So the dropdown is trying to compress something that genuinely varies enormously into five options. No dropdown can be precise about that, and one claiming to be would be lying.
Pick the Lower Category
Given the above, the practical advice is simple: if you are between two descriptions, take the lower one.
Two reasons. People consistently overestimate their activity — this is one of the best-replicated findings in the area. And the categories describe your whole week, not your best day. Three good sessions do not make a week moderately active if the other four days are spent at a desk.
Practically, it is much easier to add 200 calories after a fortnight of no change than to work out why a deficit that never existed is not working.
Sedentary is the right answer more often than people like. It is the honest choice for a desk job without deliberate training — and note it still assumes normal daily movement. It is not bed rest.
Turning TDEE Into a Plan
At roughly 7,700 calories per kilogram of fat:
| Rate | Daily change from TDEE |
|---|---|
| 0.25 kg a week | 275 |
| 0.5 kg a week | 550 |
| 1 kg a week | 1,100 |
A kilogram a week is aggressive for most people. Half that is far more sustainable and far more likely to preserve lean mass.
But hold all of it loosely. If the TDEE figure carries 10% of error before the activity guess, a 550 calorie deficit could really be 300 or 800. That is why the only reliable method is to eat at a figure for two or three weeks, watch the trend, and adjust from what actually happened.
The scale is measuring you. No equation is.
Understanding Your Result
Daily burn is the point estimate.
The honest range applies the ±10% from the underlying equation.
How it is built shows the resting figure and the factor applied to it.
Where the error actually is compares the activity gap against the equation gap, so you can see which one deserves your attention.
Worth knowing gives guidance specific to the category you chose.
When Should You Use This Calculator?
Setting a starting intake. As a hypothesis, not a prescription.
Before blaming your metabolism. Check the activity category first.
When weight change stalls. Recalculate at your new weight — TDEE falls as you do.
Comparing a deficit to a rate of loss. 7,700 calories to the kilogram.
Common Mistakes
Overstating activity. The commonest error and the largest one.
Agonising over the BMR equation. It moves the answer a fraction of what the category does.
Thinking the multiplier means exercise. NEAT is the bigger and more variable part.
Treating the figure as measured. It is an estimate on top of an estimate.
Eating at BMR instead of TDEE. That is an accidental deficit of several hundred calories.
Recalculating rather than observing. After three weeks, your own data beats any equation.
These are population estimates and can be well out for any individual. Nothing here is medical or dietary advice — speak to a doctor or registered dietitian before making significant changes to what you eat, particularly if you have any medical condition.