Your maintenance — sometimes called total daily energy expenditure — is roughly what you would eat to hold your weight steady. Every calculator that asks these six questions is answering with a population average that happens to include you; the app treats it as the fourth rung of five and prefers a measurement when it has one.
Two formulas, and when each is used
With a body-fat figure the calculation switches to Katch-McArdle, which works from lean mass and therefore does not need your age or sex at all. Without one it uses Mifflin-St Jeor. That is the same pair, in the same order, that the app falls back on — it prefers Katch-McArdle whenever Apple Health has a body-composition reading.
Neither is measured. Individual resting rates scatter around either prediction by roughly a tenth in each direction, and the activity multiplier on top of it is a single dropdown standing in for your entire waking day. That is why the app keeps asking for a better source rather than settling here.
Common questions
What are maintenance calories?
Roughly what you would eat to hold your weight steady — total daily energy expenditure under another name. Every calculator that asks these six questions answers with a population average that happens to include you, which is why the app treats it as the fourth rung of five and prefers a measurement whenever it has one.
What is the difference between BMR and TDEE?
The basal rate is what you burn at complete rest. Maintenance is that rate multiplied by an activity factor you picked from a dropdown, and the multiplication is the weak step: one number stands in for everything you do between waking and sleeping. Two people who choose the same option can genuinely be hundreds of calories apart.
Which formula does this TDEE calculator use?
Katch-McArdle when you give a body-fat percentage, because it works from lean mass and therefore needs neither your age nor your sex. Mifflin-St Jeor when you do not. That is the same pair, in the same order, that the app falls back on — it prefers Katch-McArdle whenever Apple Health has a body-composition reading.
How accurate is a TDEE calculator?
Neither formula is a measurement. Individual resting rates scatter around either prediction by roughly a tenth in each direction, and the activity multiplier adds its own error on top of that. It is a starting point, not an answer about you.
Everything you type stays in this page. There is no account, nothing is saved to your device, and no figure is sent anywhere — the arithmetic runs in your browser and is thrown away when you close the tab. The constants it uses are the ones the app runs on, published at the methodology page.