How do I calculate calories from macros?

Multiply carbs and protein by 4, fat by 9, and alcohol by 7, then add them up. 50 g carbs + 20 g protein + 15 g fat is about 415 kcal.

How many calories are in a gram of fat?

9 kcal — more than double the 4 kcal in a gram of carbs or protein.

Why do label calories not match exactly?

Labels round the figures and fiber is sometimes counted differently, so the total can differ by a few calories.

Does alcohol have calories?

Yes, 7 kcal per gram — nearly as much as fat, and with no nutritional benefit.

Health & Fitness

Food Calorie Calculator

A food’s calories come from its macronutrients. Enter the grams of carbs, protein, fat and any alcohol to get the total calories and where they come from, using the Atwater factors.

Your numbers

Result

Total calories

415

kcal

From carbskcal: 200
From proteinkcal: 80
From fatkcal: 135

Calories by macronutrient
Macronutrient	Calories	Share
Carbs (4 kcal/g)	200	48%
Protein (4 kcal/g)	80	19%
Fat (9 kcal/g)	135	33%
Alcohol (7 kcal/g)	0	0%

The Atwater factors

Each macronutrient supplies a set number of calories per gram: carbs and protein 4 kcal/g, fat 9 kcal/g, and alcohol 7 kcal/g. Total calories are the sum. For 50 g carbs, 20 g protein and 15 g fat: 50x4 + 20x4 + 15x9 = 200 + 80 + 135 = 415 kcal.

Why fat looks calorie-dense

Fat packs more than twice the calories of carbs or protein per gram, so a small amount adds up fast. That is why cooking oils and nuts are calorie-dense. Reading a label, you can check the math: multiply each macro by its factor and the totals should roughly match the stated calories.

Informational and educational result. Not a substitute for professional advice.

Frequently asked questions

Sources

Atwater general factors (energy per gram of macronutrient)

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