Two numbers come out of this: your maintenance — roughly what you would eat to hold your weight — and the daily budget that a chosen rate of loss implies. It is the same arithmetic the app uses, floor included.
What the numbers mean
The basal rate is Mifflin-St Jeor — the same formula the app falls back on when it has no body-composition reading. It predicts what you burn at complete rest, and for an individual it scatters around the prediction by roughly a tenth in either direction.
Maintenance is that rate multiplied by an activity factor you chose from a dropdown. This is the weakest link in every calculator of this kind, including this one: one number is standing in for everything you do between waking and sleeping. Two people who pick the same option can genuinely be hundreds of calories apart.
The budget is maintenance minus the deficit your chosen rate implies, at 7700 kcal per kilogram of body mass — then clamped at 1200 kcal. If the clamp bites, the result says so and tells you how much of the deficit was refused, because a budget below the floor is not a smaller plate, it is a longer timeline.
Why the app does not ask you any of this
Everything above is a prediction about a population that happens to include you. Once you have a few weeks of food entries and weigh-ins, the same arithmetic can be run backwards from what you actually ate and where your weight actually went — and that answer is about you rather than about people your size. The method page sets out how, and the four conditions it insists on before it will answer at all.
Common questions
How is the calorie deficit worked out?
A rate of loss is converted at 7700 kcal per kilogram of body mass, and the daily deficit that implies is subtracted from your maintenance estimate. It is the same arithmetic the app runs, floor included.
Why is my budget higher than the deficit I asked for?
Because the result is clamped at 1200 kcal. When the clamp bites, the page says so and tells you how much of the deficit was refused — a budget below the floor is not a smaller plate, it is a longer timeline.
Is a calorie deficit calculator accurate?
For an individual the basal rate scatters around the prediction by roughly a tenth in either direction, and the activity factor is a single dropdown standing in for a whole day. Everything here is a prediction about a population that happens to include you.
Why does the app not ask me any of this?
Because once there are a few weeks of food entries and weigh-ins, the same arithmetic can be run backwards — from what you actually ate and where your weight actually went. That answer is about you rather than about people your size.
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.