Two numbers, not one

Almost every diet argument skips a step. The number people quote — "about 2,000 calories a day" — is an average across a whole population, and it fits very few individuals. Your own requirement is built from two layers, and you can calculate both.

The first layer is your basal metabolic rate: the energy your body spends staying alive at complete rest. Breathing, circulating blood, repairing tissue, maintaining temperature. For most adults this is the largest single slice of daily energy use.

The second layer is everything else — walking, working, training, digesting, fidgeting. Multiply the first layer by an activity factor and you get your total daily energy expenditure, usually shortened to TDEE. That total is your maintenance number: eat it and your weight holds steady.

Estimating the first layer honestly

The Mifflin-St Jeor equation is the standard modern estimate. For men it starts with 10 calories per kilogram of body weight, adds 6.25 per centimetre of height, subtracts 5 per year of age, and adds 5. For women the same calculation ends with a subtraction of 161 instead. Height and age matter because tissue that is larger and younger burns more at rest.

Two caveats are worth holding onto. The equation estimates from body weight, so it overestimates for people carrying a lot of fat and underestimates for people carrying a lot of muscle. And it is an average of a population, so individual variation of a few hundred calories in either direction is normal.

Turning it into a daily target

Multiply your resting rate by an activity factor that reflects your real week, not your best week. A desk job with no deliberate exercise is sedentary; a desk job plus three or four training sessions is moderately active. Be honest here, because this is where most estimates go wrong by several hundred calories.

From that maintenance figure, the arithmetic of changing weight is straightforward. Roughly 7,700 calories equals one kilogram of body fat, so a daily deficit of 500 calories trends toward about half a kilogram a week. That is a pace most people can hold without feeling starved, which is why it is the usual starting recommendation. Larger deficits move the scale faster but rarely last.

Then decide where the calories come from. Protein is worth setting first because it protects muscle when you are in a deficit; a common range is 1.6 to 2.2 grams per kilogram of body weight. Fat covers hormones and satiety, usually 0.8 to 1 gram per kilogram. Carbohydrate takes what is left, which is exactly how a macro split is calculated rather than guessed.

  • Set protein from body weight, not from a percentage
  • Set fat from body weight for hormone and satiety needs
  • Fill the remainder with carbohydrate for training energy
  • Recheck every few kilograms of weight change, since the target moves with you

The calorie calculator produces the daily target and the macro split together. If you have not yet worked out maintenance, start with the TDEE calculator to get that baseline, then use the macro calculator once your target is settled. Treat the first two weeks as a test: if your weight is not moving as predicted, adjust by 100 to 200 calories rather than rewriting the whole plan.