Measured, not guessed
Every calorie app you have used gave you a number on day one. Almost none of them have ever checked whether it was true.
The brochure figure
Every car has a fuel economy figure on the brochure. It was worked out in a lab, on a representative car, under conditions nobody drives in. Nobody believes it. Everybody knows their own car does worse, or better, and they know it because the trip computer tells them what the car actually used over the miles they actually drove.
Your calorie target is a brochure figure. It comes from an equation built on a population, using your height, your weight, your age and your sex, and then multiplied by an activity level you picked from a dropdown. It is an average person's answer, handed to you.
Kriterion is the trip computer. It watches what you ate and what the scale did, and works out what you actually burned.
How you can measure something you cannot see
You cannot watch your body burn energy. But you can watch two things that are easy to measure, and the answer falls out of the gap between them.
- What went in. The food you logged.
- What happened to you. What the scale did over the same stretch.
Eat roughly the same for a couple of weeks. If your weight holds steady, that intake is your maintenance. If it drifts down, you were under it, and by how much tells you the size of the gap. That is the whole idea, and it is the same arithmetic whether you are gaining, losing or holding.
The hard part is not the sum. It is that weight is noisy: water, salt, the cycle, what is still in your gut. Most of the work is separating the signal from that noise without throwing away the days that count.
The number that tells you whether to believe it
Kriterion prints a margin beside the figure. Not as a disclaimer. As the point.
An equation has nothing to be uncertain about. It will give the same answer forever, on the same inputs, with no idea whether it was right. So a range is the tell that something actually measured you: you only get to be uncertain about a thing you tried to observe.
That range tightens as you log, and it widens if you stop, because an app that has not heard from you for a fortnight should say it is less sure rather than pretend otherwise.
It marks its own homework
Here is the part no calorie app does. Kriterion replays what it believed earlier against what your scale actually did afterwards, and tells you whether it was running ahead, behind or close.
That matters because no app can prove its calorie number is true. Nobody can. What an app can prove is whether acting on the number worked, which is the only question you actually care about. An app that sets a target every day for a year and never once checks it is a teacher who sets homework and never marks it.
What this costs, honestly
The free tier gives you a calorie target the way everyone else does: a formula, worked from your own body. It is a reasonable place to start and it is what almost every app in the category charges for.
The measuring is Premium. The burn rate worked from your own data, the margin beside it, and the self-check against your results. That is the line, and it is the line because that part is the product.
It also takes time before it can say anything, which is a real cost and not a small one. Here is what that actually looks like, week by week, including what you get in the meantime.