Calories from Macros Calculator
Calculate total calories from grams of protein, carbohydrates, and fat.
Total Calories
kcal
Calorie Breakdown
Percentage of Total Calories
Protein
Carbs
Fat
Alcohol
The Atwater 4-4-9 Factors
Food energy is calculated using the Atwater system, which assigns an average energy value to each macronutrient. Multiply the grams of each nutrient by its factor and add them together to get total calories:
Calories = (4 × Protein) + (4 × Carbs) + (9 × Fat) + (7 × Alcohol)
- Protein – 4 kcal per gram.
- Carbohydrates – 4 kcal per gram.
- Fat – 9 kcal per gram, more than twice as energy-dense as protein or carbs.
- Alcohol – 7 kcal per gram, often overlooked on nutrition labels.
How to Read Nutrition Labels
A nutrition label lists the grams of protein, total carbohydrate, and fat per serving. You can use those numbers directly in this calculator to verify the stated calorie count or to compare foods.
- Check the serving size first. All values on the label refer to one serving, so multiply by the number of servings you actually eat.
- Total carbohydrate includes fiber and sugar. The standard Atwater factor of 4 kcal/g is applied to total carbohydrate; fiber contributes fewer usable calories in reality.
- Calorie counts are rounded. Labels round to the nearest 5 or 10 calories, so a small difference from this calculator is normal.
- Don't forget alcohol. Beverages list grams of alcohol indirectly; at 7 kcal/g it can add up quickly.
Understanding Macro Balance
The percentage of calories from each macronutrient describes the balance of your diet. There is no single ideal split, but most general guidelines fall within these ranges:
Protein
10–35%
Builds and repairs tissue, supports muscle, and increases satiety.
Carbohydrates
45–65%
The body's primary energy source for exercise and brain function.
Fat
20–35%
Essential for hormones, nutrient absorption, and cell membranes.