How to Calculate Calories from Grams (Atwater Factors)
Calories use Atwater factors: carbs and protein 4 kcal/g, fat 9 kcal/g, alcohol 7 kcal/g. So 20 g of fat = 9 x 20 = 180 kcal, and 55 g of carbs = 4 x 55 = 220 kcal.
Open the interactive Everyday Lifestyle tool →Key facts
| Carbs / protein | 4 kcal/g |
|---|---|
| Fat | 9 kcal/g |
| Alcohol | 7 kcal/g |
| 20 g fat | 180 kcal |
| kcal to kJ | 1 kcal = 4.184 kJ |
Frequently asked questions
How many calories in 20 g of fat?
180 kcal: fat is 9 kcal/g, so 9 x 20 = 180 kcal.
How do I total the calories of a food?
Add 4 x carbs(g) + 4 x protein(g) + 9 x fat(g), plus 7 x alcohol(g) if present.
How do I convert kcal to kJ?
Multiply by 4.184. 100 kcal = 418.4 kJ.
Related pages
The calculations on this page are estimates based on common general-purpose formulas. They are not medical advice -- consult a doctor or other qualified professional for decisions about your health.
Calories from Grams (Atwater) is part of Everyday Lifestyle on GOAT Lab — a free reference you can use without signing up, and it works offline. Open the tool above for any custom value.
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