# Grams to Calories Calculator

URL: https://speedycalculator.com/calculators/conversion/grams-to-calories/
Last updated: 2026-10-25

> The grams to calories calculator converts grams of carbohydrate, protein, fat and alcohol into kilocalories using the Atwater factors (4, 4, 9 and 7 kcal per gram), and shows where the calories come from.

## Inputs

- Carbohydrate (g)
- Protein (g)
- Fat (g)
- Alcohol (g)

## Results

- Total energy
- In kilojoules
- From carbohydrate
- From protein
- From fat
- From alcohol
- Share from fat

## Formula

```
kcal = 4 × carbs + 4 × protein + 9 × fat + 7 × alcohol
```

## Explanation

Nutrition labels list macronutrients in grams. The general Atwater factors convert those grams into energy: fat has more than twice the energy per gram of carbohydrate or protein.

### How to use the Grams to Calories Calculator

- **Carbohydrate**
- **Protein**
- **Fat**
- **Alcohol**
- Every result field is editable: type into **Total energy** and **Fat** plus every other field update to match.

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Each macronutrient’s grams are multiplied by its energy factor and the results are added.

### Inputs explained

FieldWhat to enterCarbohydrateIn gProteinIn gFatIn gAlcoholIn g

### What each result means

- **Total energy** = 4×[Carbohydrate] + 4×[Protein] + 9×[Fat] + 7×[Alcohol]
- **In kilojoules** = (4×[Carbohydrate] + 4×[Protein] + 9×[Fat] + 7×[Alcohol]) × 4.184
- **From carbohydrate** = 4×[Carbohydrate]
- **From protein** = 4×[Protein]
- **From fat** = 9×[Fat]
- **From alcohol** = 7×[Alcohol]
- **Share from fat** = 9×[Fat] ÷ (4×[Carbohydrate] + 4×[Protein] + 9×[Fat] + 7×[Alcohol]) × 100

### Example values

How the main result changes when **Fat** changes and everything else stays at the example values above:

Fat (g)Total energy (kcal)53257.5347.51037012.5392.51541520460

## Worked example

Inputs — Carbohydrate: 50 g; Protein: 20 g; Fat: 10 g; Alcohol: 0 g.

Results — **Total energy = 370 kcal**; In kilojoules = 1,548 kJ; From carbohydrate = 200 kcal; From protein = 80 kcal; From fat = 90 kcal; From alcohol = 0 kcal; Share from fat = 24.3 %.

## FAQ

**How many calories in a gram of fat?**
9 kcal.

**How many calories in a gram of carbohydrate?**
4 kcal.

**Does fibre count?**
Labels often count fibre at about 2 kcal/g; this calculator uses the general factor for total carbohydrate.

**What formula does the Grams to Calories Calculator use?**
kcal = 4 × carbs + 4 × protein + 9 × fat + 7 × alcohol.


## Sources

- [FAO – Food energy: methods of analysis and conversion factors](https://www.fao.org/3/y5022e/y5022e00.htm)