Macro Calculator
Calculate optimal protein, carb, and fat daily grams.
This macro calculator splits your daily calorie target into protein, carbohydrate, and fat grams based on your goal - weight loss, maintenance, or muscle gain. It works as a calorie and macro calculator in one step, so you don't need to calculate calories separately before figuring out how many carbs per day to eat.
Enter your calorie target and goal, and the calculator returns grams of protein, carbs, and fat to hit.
Worked Calculation Examples
| Scenario | Result | Calculation Step |
|---|---|---|
| 2,000 kcal, 40/30/30 split (protein/carb/fat) | Protein 200g · Carbs 150g · Fat 67g | Protein = 2,000 × 0.40 ÷ 4 = 200g. Carbs = 2,000 × 0.30 ÷ 4 = 150g. Fat = 2,000 × 0.30 ÷ 9 ≈ 67g. |
| 2,500 kcal, 30/45/25 split (muscle-gain style) | Protein 188g · Carbs 281g · Fat 69g | Protein = 2,500 × 0.30 ÷ 4 = 187.5g. Carbs = 2,500 × 0.45 ÷ 4 = 281.25g. Fat = 2,500 × 0.25 ÷ 9 ≈ 69.4g. |
How Macros Are Split from Total Calories
Protein and carbohydrates each provide about 4 calories per gram, while fat provides about 9 calories per gram. A macro split - like 40% protein, 30% carbs, 30% fat - is converted to grams by multiplying total calories by each percentage, then dividing by the calorie-per-gram value for that macronutrient. The standard calorie values used in this conversion - 4 calories per gram for protein and carbohydrates, 9 for fat - were established by American chemist Wilbur Atwater in the late 19th century through direct combustion experiments measuring the energy released by different foods, and his figures remain the basis for nutrition labeling worldwide.
Choosing Macros for Fat Loss vs. Muscle Gain
Diets aimed at macros for fat loss typically keep protein high (to preserve muscle in a calorie deficit) while moderating carbs and fat. Muscle-gain macro splits usually keep protein high as well but allow more total calories, often with a higher carbohydrate share to fuel training performance.
How to Use the Macro Calculator
- Open the Macro Calculator and enter the values requested in the input fields.
- Check the units, percentages, dates, or time periods before reading the answer.
- Review the instant result and adjust any value to compare another scenario.
- Use the formula, example, and FAQs below to understand how the macro calculator works.
Frequently Asked Questions
How many carbs per day should I eat?
It depends on your total calories and macro split - a common starting point is 30-50% of calories from carbs, translated into grams by dividing that calorie share by 4 (calories per gram of carbohydrate).
How do I calculate my macros for weight loss?
Start from your calorie deficit target, then split it into grams of protein (kept relatively high to preserve muscle), carbs, and fat according to a chosen percentage split.
Why is protein calculated differently for macros vs weight loss goals?
Protein needs scale more with body weight and training goals than with total calories, so many macro plans set protein grams first (per kg of body weight) and split the remaining calories between carbs and fat.
How do I use this macro calculator?
Enter the known values, review the units or settings, and the calculator updates the result instantly. The formula and example on this page show how the answer is produced.
What does the Macro Calculator calculate?
Calculate optimal protein, carb, and fat daily grams. It is designed for fast browser-based calculations without sign-up, downloads, or manual spreadsheet setup.
What formula does this macro use?
The formula is: Protein (g) = Calories × Protein% ÷ 4; Carbs (g) = Calories × Carb% ÷ 4; Fat (g) = Calories × Fat% ÷ 9. Calories is your total daily calorie target, and each percentage is the share of that target assigned to protein, carbs, or fat. Protein and carbohydrates each supply about 4 calories per gram, while fat supplies about 9 calories per gram, so dividing the calorie share for each macro by its own calories-per-gram value converts it into grams.
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Last updated: September 29, 2026.