If you put the same numbers into three calculators and got three answers, that isn't a bug. Several formulas are in common use, and most of the difference comes from how they estimate activity. Here is how it actually works and what to do with the result.
What you'd burn lying in bed all day. The standard formula is Mifflin-St Jeor:
| Factor | Fits someone who... |
|---|---|
| 1.2 | works at a desk, trains rarely |
| 1.375 | trains 1–3 times a week |
| 1.55 | trains 3–5 times a week |
| 1.725 | trains 6–7 times, or has a physical job |
This is where most of the error lives. People pick a multiplier that's too high — three gym sessions a week alongside a desk job and a mostly seated day is 1.375, not 1.55. One step up is 200–300 calories a day, which is roughly the entire deficit. When in doubt, take the lower one and adjust from real results.
| Goal | Target |
|---|---|
| Losing weight | 15–20% below your burn |
| Maintaining | equal to your burn |
| Building | 10–15% above your burn |
This is the usual reason for a third-month plateau, not a "damaged metabolism". The calories for weight loss guide goes into more detail.
These formulas are statistical estimates and can be off by 10% in either direction for any given person. They know nothing about your body composition, genetics or how much you fidget.
So treat it properly: the calculator gives a starting point, reality gives the answer. Track two or three weeks, and if the scale isn't moving as expected, adjust by 100–150 calories and check again. After a round or two you'll have your real number, which is worth more than any formula.
Achalti works out your target automatically from your profile, updates it as your weight changes, and factors in steps and workouts synced from Apple Health or Health Connect.
This guide is general information based on mainstream nutrition recommendations. It is not personal medical or dietary advice.