Do I have to hit macros exactly?

No. Within ±5–10 g per macro daily is fine; weekly averages drive outcomes, not individual days.

Why does fat have 9 kcal per gram?

Fat is chemically more reduced than carbohydrate or protein, so oxidation releases more energy per gram; the Atwater convention quantifies this.

Are low-carb or low-fat better?

Head-to-head trials show similar fat loss at equal protein and calories. Adherence, not macro philosophy, predicts success.

Health

Macro Calculator

What this does

Split your daily calories into carbohydrate, protein and fat gram targets using adjustable percentages and standard energy densities.

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Runs in your browser

How to use it

Using the macro calculator

01
Enter your calorie target
Use your TDEE to maintain, or the deficit calculator’s target to lose.
02
Pick your percentages
Adjust each macro’s share; they must total 100% or the calculator will ask you to rebalance.
03
Log against grams
Track foods by gram targets rather than obsessing over daily percentages; labels list grams.

Good to know

Protein first, then split the rest

Most evidence supports setting protein relative to body weight (1.2–2.2 g/kg depending on goals), letting fat fall no lower than ~20% for hormone health, and filling remaining calories with carbohydrate. Percent-based splits are a convenient approximation of that logic.

What 40/30/30 looks like on a plate

At 2,000 kcal that is roughly oatmeal and fruit at breakfast, a palm-sized protein portion at each meal, rice or potatoes around training, olive oil or nuts for fats; ordinary food arranged consistently, nothing exotic.

Common splits by goal

Balanced maintenance: 40% carb / 30% protein / 30% fat.
Endurance training blocks: up to 50–60% carbohydrate.
Higher-protein fat-loss phases: 30–35% protein with reduced carbs.

How it's calculated

The math behind this calculator

Carbs g = kcal × % ÷ 4 Protein g = kcal × % ÷ 4 Fat g = kcal × % ÷ 9

Each macro’s calorie share divides by its energy density; 4 kcal per gram for carbohydrate and protein, 9 kcal per gram for fat; converting your percentage split into concrete daily gram targets you can log against food labels.

The default 40/30/30 split is a balanced starting point popular in sports nutrition; endurance athletes often push carbohydrates toward 50%, while higher-protein cuts favour 35% protein.

Assumptions & limitations

Gram targets use Atwater factors (4/4/9); fibre and alcohol calories are not modeled.
Percentages must sum to exactly 100%.
Targets are daily averages; hitting them precisely every single day is unnecessary.

Worked example

On a 2,000 kcal diet at the classic 40/30/30 split you would aim for about 200 g of carbs, 150 g of protein and 67 g of fat each day.

FAQ

Frequently asked questions

Do I have to hit macros exactly?: No. Within ±5–10 g per macro daily is fine; weekly averages drive outcomes, not individual days.
Why does fat have 9 kcal per gram?: Fat is chemically more reduced than carbohydrate or protein, so oxidation releases more energy per gram; the Atwater convention quantifies this.
Are low-carb or low-fat better?: Head-to-head trials show similar fat loss at equal protein and calories. Adherence, not macro philosophy, predicts success.

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