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Macro Nutrient Split Calculator

First calculate protein grams by multiplying body weight (kg) with the desired protein per kilogram. Convert that to calories using 4 kcal per gram. Determine fat calories as the chosen percentage of total daily calories and divide by 9 kcal/g to get grams. Subtract protein and fat calories from the total; whatever remains goes into carbohydrates, which are computed by dividing the remaining calories by 4 kcal/g. Finally round each macro value to the nearest whole gram.

Total calories you plan to consume each day.
Your current body weight in kilograms.
Grams of protein you want per kilogram of body weight; commonly 2.0–3.0 g/kg for CrossFit athletes.
Desired percentage of total calories from fat (e.g., 25 for 25%).
Select your training goal to set sensible defaults.

What it is

The Macro Nutrient Split Calculator is a precision tool that converts a user’s total daily calorie target into exact gram‑amounts of protein, fat, and carbohydrates tailored for muscle gain or weight loss. It applies the fundamental science of energy density—protein and carbs provide 4 kcal/g while fat offers 9 kcal/g—and accounts for body weight through grams per kilogram of protein. By specifying a target fat percentage, the calculator automatically allocates remaining calories to carbs, ensuring the sum matches the desired total. This enables athletes to plan meals with exact macro targets, crucial for optimizing recovery, muscle hypertrophy, and body recomposition.

How to use it

Enter your daily calorie goal, current weight in kilograms, preferred protein per kg, and target fat percentage. Optionally pick your training goal; defaults will adjust suggested ranges but don’t alter the calculation. Click Calculate to see grams of protein, fat, and carbs displayed as whole numbers. Use those values when shopping or portioning meals for daily compliance.

Worked example

First, compute protein grams: 85 kg × 2.5 g/kg = 212.50 g, rounded to 213 g. Protein calories equal 213 g × 4 kcal/g = 852 kcal. Next, fat calories are the chosen 25% of total calories: 2800 × 0.25 = 700 kcal. Fat grams come from dividing fat calories by 9 kcal/g: 700 ÷ 9 ≈ 77.78 g, rounded to 78 g. Remaining calories for carbs are 2800 − 852 − 700 = 1248 kcal. Carbohydrate grams equal 1248 ÷ 4 = 312 g, exactly as shown in the outputs.

Inputs

  • Daily Calories (kcal): 2800
  • Body Weight (kg): 85
  • Protein per kg (g/kg): 2.5
  • Target Fat %: 25
  • Goal: 0

Result

  • Protein (g): 213
  • Fat (g): 78
  • Carbohydrates (g): 312

Frequently asked questions

Can I change the protein per kilogram value after calculation?

Yes – simply enter a new protein-per-kg value or choose your goal to reset it automatically. The calculator will re‑compute all macro values instantly.

Why might my carb grams be lower than expected?

Carb grams are derived from whatever calories remain after subtracting protein and fat calories, so if either macronutrient is set high or calories are low, carbs necessarily drop accordingly. Rounding each macro to the nearest whole gram also slightly affects the final sum.

How does the calculator handle negative carb targets?

All inputs must produce a non‑negative carbohydrate target; if protein and fat calories exceed total calories (e.g., unrealistic settings), the tool will raise an error indicating invalid macro distribution rather than returning nonsensical values.

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