Why every calorie calculator gives a different number
Enter the same details into three calculators and you will get three answers, often a few hundred calories apart. That is not a mistake. Each uses a different equation to estimate your basal metabolic rate, and a different set of activity multipliers on top. Ours uses the revised Harris-Benedict equation, one of the most established, then a standard activity matrix.
Treat the number as a starting point, not a fixed truth. Your real maintenance calories only become clear once you eat at a set level for two to three weeks and watch what your weight does. If it holds, that is your maintenance. If it drifts, adjust by a couple of hundred calories and watch again.
Why protein comes first
Most calculators treat protein as an afterthought. We set it first, because it is the macro that decides whether you keep muscle while you lose fat, or build it while you gain. We estimate your lean mass from your body type, set protein against that, then fit fat and carbohydrate around it.