How many calories should I eat?

Every calculator gives you a different number and all of them are estimates. Here is where the number comes from, and how to replace it with one that is actually yours.

Where the number comes from

It starts with basal metabolic rate — what you burn doing nothing — usually from the Mifflin-St Jeor equation, which takes your weight, height, age and sex.

That gets multiplied by an activity factor, somewhere between about 1.2 for sedentary and 1.9 for very active, to give total daily energy expenditure. Then a deficit or surplus is applied.

Two of those three steps are guesses. The equation has meaningful error between individuals, and the activity multiplier is a self-assessment most people get wrong.

Typical deficits, and why bigger is not better

A deficit of roughly 15-25% of maintenance is the usual range for fat loss. Larger deficits do lose weight faster and cost more muscle, more adherence and more of the training quality that makes the result hold.

For most people that lands somewhere between 300 and 700 calories below maintenance. Note the width of that range — it is why the calculator number is a starting point, not an answer.

The two-week correction that actually works

Pick the calculator number. Eat it consistently for two weeks, logging honestly.

Track weight every morning and use the weekly average, not any single day. Daily weight is mostly water, food volume and salt.

Compare the two weekly averages. If the trend is not moving the way you intended, adjust by 10% and repeat.

After one round of this you have a maintenance figure based on your own body rather than a population equation — which is worth more than any calculator.

Protein first, then the rest

Whatever the calorie number is, protein does the work of keeping muscle while you lose fat. Set it first and let carbohydrate and fat fill the remainder to preference.

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