How are macros calculated from calories?

Each macro provides a known number of calories: protein 4 kcal/g, carbohydrate 4 kcal/g and fat 9 kcal/g (the Atwater values). The calculator splits your calorie target by the chosen percentages, then divides each share by its kcal-per-gram to get grams.

What is a good macro split?

A balanced 30/40/30 (protein/carbs/fat) suits most people. Higher protein (40/30/30) helps with muscle retention in a deficit; lower carb (40/20/40) suits some fat-loss plans; and endurance athletes often run higher carbs (25/55/20).

How much protein do I need?

General fitness guidance is roughly 1.6–2.2 g of protein per kg of body weight per day. The high-protein presets here lean toward that range, but individual needs vary — adjust the split to hit your target grams.

Is this medical advice?

No. This is an educational calculator, not medical or dietary advice. Consult a qualified professional for a plan tailored to you. All calculations run locally in your browser.

Macro Split Calculator

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The Macro Split Calculator converts a daily calorie target into grams of protein, carbohydrate and fat for the ratio you choose. It is the quick bridge between “I want 2,000 calories” and “so that’s how many grams of each macro” — and it runs entirely in your browser.

How the maths works

Each macronutrient has a known energy density (the Atwater values):

Macro	Calories per gram
Protein	4 kcal/g
Carbohydrate	4 kcal/g
Fat	9 kcal/g

The calculator splits your calorie target by the chosen percentages, then divides each portion by its kcal-per-gram to get grams. For example, 2,000 kcal on a 30/40/30 split gives 150 g protein, 200 g carbs and ~67 g fat.

Choosing a split

Balanced (30/40/30) — a sensible default for most people.
High protein (40/30/30) — supports muscle retention in a calorie deficit.
Low carb (40/20/40) — favoured by some fat-loss approaches.
Endurance (25/55/20) — more carbohydrate to fuel long training.

This is educational information, not medical advice — consult a professional for a personalised plan. Everything is calculated locally in your browser.