What is the Nutrition Calculator?

The Nutrition Calculator converts between macronutrient grams (protein, fat, carbohydrates) and their caloric value. It uses standard Atwater factors: carbohydrates and protein provide 4 kcal/g, fat provides 9 kcal/g. Useful for meal planning and calorie tracking.

How to Use the Nutrition Calculator

Select mode: 'Grams → Calories' to calculate calories from macronutrient grams, or 'Calories → Grams' for reverse conversion. Enter values for each macronutrient. The calculator shows total calories, per-macro breakdown, and percentage distribution.

Why Use the Nutrition Calculator?

• Quick calorie calculation from macronutrient data
• Plan macronutrient ratios for sports nutrition
• Monitor percentage distribution of macronutrients in your diet
• Convert calorie recommendations into grams of specific nutrients

Frequently Asked Questions about Nutrition

Where do the 4/4/9 kcal/g values come from?

These are Atwater factors, established in the early 20th century by American chemist Wilbur Atwater. They represent average energy values: carbohydrates — 4 kcal/g, protein — 4 kcal/g, fat — 9 kcal/g. These are the international standard in nutrition science.

What is the optimal macronutrient ratio for athletes?

It depends on the sport and goals. For endurance athletes: 55-65% carbs, 20-25% fat, 15-20% protein. For strength sports: 40-50% carbs, 25-30% fat, 25-35% protein. Before long events, carb percentage may increase to 70%.

Why does fat contain more calories?

Fat molecules contain more hydrogen and carbon atoms relative to oxygen compared to carbs and protein. Oxidizing these atoms releases more energy, making fat the most energy-dense macronutrient at 9 kcal per gram — more than double that of carbs or protein.