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How many calories and protein should i eat a day?

How many calories and protein should i eat a day: calculation method, required inputs, worked check, limitations and a link to Calorie Calculator. Reviewed 2...

By Uddhav Gopani, FounderPublished 25 September 2026Reviewed 25 September 2026

Calories and protein are set by different rules, so compute them separately. Calories come from energy balance — your maintenance total minus any planned deficit. Protein comes from body mass: roughly 1.2–2.0 g per kg for active adults, with the higher end used during a deficit or strength training.

What this specific question is asking

A daily answer looks like: maintenance calories (BMR × activity factor) adjusted for your goal, paired with a protein floor in grams. Hitting the protein target while undershooting calories is the combination that preserves muscle during weight loss — which is why the two numbers belong on the same page but never in the same formula.

Cross-check the pair against each other: if your calorie target is low but protein lands under 1.2 g/kg, the plan trades muscle for speed. Adjust protein first, then set calories around it — not the reverse.

Inputs to verify

Verify weight (kg) before calculation; if this value uses a different unit, period or definition, convert or restate it first.
Verify height (cm) before calculation; if this value uses a different unit, period or definition, convert or restate it first.
Verify age (years) before calculation; if this value uses a different unit, period or definition, convert or restate it first.
Verify sex before calculation; if this value uses a different unit, period or definition, convert or restate it first.
Verify activity level before calculation; if this value uses a different unit, period or definition, convert or restate it first.
Verify goal before calculation; if this value uses a different unit, period or definition, convert or restate it first.

Step-by-step check

Enter your weight, height, and age first.
Pick your sex and activity level.
Choose whether you want to lose, maintain, or gain.
Press Calculate to see your daily calorie target.

Worked example and sanity check

As a worked reference for “How many calories and protein should i eat a day”, Worked example Maintenance calories = BMR × an activity factor. With a BMR of 1,500 kcal and a 'lightly active' factor of 1.375, daily maintenance is ≈ 2,063 kcal . A moderate 500 kcal deficit (~1,563 kcal) is often used as a starting point for gradual change. Individual needs vary widely — treat this as a rough guide and consult a qualified professional for a personalised plan.

Interpreting the result

The output is only useful against a reference. The example's BMR × an activity factor gives that reference: your own result should be explainable against it — larger or smaller for a reason you can name. Read the magnitude before the decimals: a result ten times too large or small almost always means a unit or period slipped, not that the formula failed.

Reviewed 25 September 2026

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Use the Calorie Calculator

Open Calorie Calculator

Common questions

Which inputs matter most for how many calories and protein should i eat a day?

The key inputs are Daily calories (kcal), Macro split. Match their units and periods before using Macro Calculator.

How can I check an answer for how many calories and protein should i eat a day?

Run the example exactly as written, then vary weight (kg) alone. A result that tracks that change predictably tells you the setup — units, periods, definitions — is correct.

When should I recalculate how many calories and protein should i eat a day?

Recalculate whenever any input's basis changes: a new measurement, a revised rate or threshold, a different period convention, or an updated policy figure.