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
| Field | What to enter |
|---|---|
| Carbohydrate | In g |
| Protein | In g |
| Fat | In g |
| Alcohol | In 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) |
|---|---|
| 5 | 325 |
| 7.5 | 347.5 |
| 10 | 370 |
| 12.5 | 392.5 |
| 15 | 415 |
| 20 | 460 |
Formula
kcal = 4 × carbs + 4 × protein + 9 × fat + 7 × alcoholWorked 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 %.
Frequently asked questions
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.