Macro Calculator
Turn calories and a split into grams of protein, carbs and fat.
Runs entirely in your browser — nothing you enter is uploaded or sent to a server.
This converts a calorie figure you supply into grams — it doesn't decide what your calorie figure or your split should be. Protein, carbohydrate and fat targets depend on your training, health and any medical conditions, and choosing them is a conversation for a dietitian or a doctor. Real foods also vary from the standard 4/4/9 factors, particularly anything high in fibre. Read our full disclaimer.
About this tool
Macronutrient targets are usually given as percentages — 30/40/30 and so on — but you can't eat a percentage, so at some point everyone converts them into grams and gets the arithmetic slightly wrong. This does the conversion properly using the Atwater factors: 4 calories per gram of protein, 4 per gram of carbohydrate and 9 per gram of fat. Pick one of the common splits or type your own, and it shows the grams alongside the calories each macro accounts for, so you can see the whole thing add back up. If your custom percentages don't total 100, it scales them rather than silently losing or inventing energy — the grams always account for exactly the calories you entered.
Example
2,000 kcal on a 30/40/30 split works out to 150 g of protein, 200 g of carbohydrate and about 67 g of fat.
How to use
- 1Enter the daily calorie figure you're working to.
- 2Pick one of the named splits, or choose Custom and set your own percentages.
- 3Read the grams for each macronutrient, with the calories each accounts for.
Features
- Atwater factors — 4, 4 and 9 kcal per gram — shown next to each row.
- Four common splits, plus fully custom percentages.
- Percentages that don't total 100 are scaled, so no calories go missing.
- A converter, not a coach: it never suggests which split you should use.
Frequently asked questions
What are the 4/4/9 numbers?
They're the Atwater factors — the average metabolisable energy in a gram of each macronutrient. Protein and carbohydrate give roughly 4 kcal per gram and fat about 9, which is why fat targets look small in grams next to carbohydrate ones. Alcohol, for completeness, is about 7.
Which split should I use?
We deliberately don't answer that. The right split depends on what you're training for, what you enjoy eating, and any medical conditions in play — it's a question for a dietitian, not a calculator. The named options here are the ones people commonly ask about, offered so you can convert a split you've already chosen.
My percentages don't add up to 100. What happens?
They're scaled proportionally to fit the calorie figure you entered, so the grams still account for every calorie. That means you can enter a ratio like 3:4:3 directly and get the same answer as 30/40/30.
Are the gram figures exact for real food?
They're exact for the standard factors, which is the best any calculator can do. Actual foods vary: fibre contributes fewer calories than the carbohydrate number implies, and food labels round. Treat the output as a target to plan against rather than a precise measurement of a meal.
Where do I get the calorie figure to put in?
Our Calorie Calculator estimates the energy you use in a day from the Mifflin–St Jeor equation. Whether the number you plan around should match that, or sit above or below it, is a decision to make with a professional.
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