What does this tool do?
The Macro Calculator turns your daily calorie target into grams of protein, carbs, and fat. It offers ready-made presets for weight loss, maintenance, muscle gain, and keto, plus a custom mode where you set the percentages yourself. It's quick and practical for anyone planning their nutrition.
How to use it
- Enter your values into the fields.
- The result is calculated instantly.
- Read or copy the result.
How calories convert to grams
The calculation relies on each macronutrient's energy density: every gram of protein and carbohydrate provides 4 calories, while every gram of fat provides 9. The tool first finds each macro's calorie share from your chosen percentage, then divides by the matching factor to get grams. For example, 30% protein of a 2,000-calorie target equals 150 grams. Each card shows the grams, the percentage, and the calorie total together so the breakdown is easy to read.
Presets and custom mode
Maintenance uses a 30/40/30 split, Weight Loss leans higher on protein, Muscle Gain balances more carbohydrate, and Keto pairs very low carbs with high fat. These presets are a starting point; choose the Custom mode to set protein, carb, and fat percentages yourself with three sliders. If the total doesn't reach 100%, the tool warns you, so your distribution always stays consistent and the gram figures remain meaningful.
Frequently asked questions
Why are protein 4 and fat 9 calories per gram?
These are the standard Atwater factors: protein and carbohydrate carry about 4 calories per gram, and fat carries 9. The calculation is based on these values.
What happens if my custom percentages don't add up to 100?
The tool shows the total with a red warning. Results are still calculated, but it's recommended to adjust the sliders to 100% so your macro split stays accurate.
Does this tool calculate my daily calorie needs?
No, it divides the calorie target you enter into macros. You should first determine your total calorie needs with a TDEE or calorie calculator and enter that figure here.
Is Macro Calculator free?
Yes. Macro Calculator and all 300+ tools on MagmaNex are completely free with no signup or account required.
Is my data safe?
Yes. Everything runs locally in your browser. The data you enter is never sent to a server, stored, or shared.
Does it work on mobile?
Yes. Macro Calculator works on phones, tablets and desktops — no app download needed.
🔒 Privacy: everything runs in your browser, your data is never sent to a server.