There is a number of calories at which your weight stays where it is. Eat below it and you lose weight; eat above it and you gain. Everything else — meal timing, which foods, how many meals — sits on top of that one fact, and none of it replaces it.
The useful question is not "how many calories should I eat", which has no single answer, but "what is my maintenance number, and how far below it can I live for a few months without hating my life".
Step one: find maintenance
Your maintenance figure is your total daily energy expenditure, and there is a whole article on how it is built: BMR vs TDEE. The short version is that a formula estimates what your body burns at rest, and a multiplier accounts for how much you move.
The estimate you get is a starting point, not a measurement. Published equations were fitted to populations, and you are one person. Expect it to be within roughly a couple of hundred calories of your real number, and expect to correct it from the scale over two or three weeks rather than trusting it outright.
Step two: pick a deficit you can hold
A kilogram of body fat stores somewhere around 7,700 kcal. That is the arithmetic behind every pace target you have seen: a deficit of 500 kcal a day is about 3,500 kcal a week, which is roughly half a kilogram.
That number is where most plans go wrong, because it is treated as a dial that goes as high as you like. It does not. A larger deficit does not mean proportionally faster progress — it means more hunger, worse training, and a much higher chance you abandon the whole thing in week three. A deficit you follow for twelve weeks beats a deficit you follow for nine days, every time.
A reasonable range for most people is something between 0.25% and 0.75% of body weight per week. The lower end feels like almost nothing day to day and is remarkably easy to sustain; the upper end is noticeable and needs more planning around protein and sleep.
Step three: correct from the scale, not the spreadsheet
Weigh yourself on the same days under the same conditions, and compare weekly averages rather than individual mornings. Day-to-day weight is mostly water, glycogen and what is currently in transit; a single reading tells you almost nothing.
After two or three weeks you will have enough data to know whether your estimate was right. If the average has not moved and you have been logging honestly, your maintenance estimate was too high — lower intake modestly and hold it for another fortnight. If you are dropping faster than you planned, eat a little more.
The part nobody wants to hear
Almost all of the failure in calorie counting is in the logging, not in the maths. The estimate is easy; the honesty is hard. Oils, sauces, the handful of something while cooking, the weekend that quietly runs 900 kcal over — those are what close a deficit that looks perfect on paper.
That is why the first thing worth building is not the perfect target but the habit of recording every day. A rough number logged consistently beats a precise number logged three days a week, and it is not close.
If you want to know how far off eyeballing really is, we measured it. And once your calorie target is steady, macros are the next layer.