Contents
4, 9, 4 and also 7
- 1 g of protein: 4 kcal.
- 1 g of fat: 9 kcal.
- 1 g of carbohydrate: 4 kcal.
- 1 g of alcohol: 7 kcal.
These factors are called the Atwater system, after the American chemist who derived them in the late 19th century. Food labels in Russia, the EU and the US are calculated with them. Fat gives more than twice as much energy per gram, which is why oil, nuts and cheese eat up a daily target so fast.
Table: calories in grams of protein, fat and carbohydrate
| Grams | Protein, kcal | Fat, kcal | Carbs, kcal |
|---|---|---|---|
| 1 g | 4 | 9 | 4 |
| 10 g | 40 | 90 | 40 |
| 30 g | 120 | 270 | 120 |
| 50 g | 200 | 450 | 200 |
| 100 g | 400 | 900 | 400 |
| 150 g | 600 | 1,350 | 600 |
| 200 g | 800 | 1,800 | 800 |
| 300 g | 1,200 | 2,700 | 1,200 |
And the other way round: 1,000 kcal is 250 g of protein or carbohydrate, or 111 g of pure fat.
Other nutrients
Besides the big three, food contains a few substances with factors of their own, and although there aren't many of them, they're the reason a label sometimes doesn't add up:
| Nutrient | kcal per 1 g | Found in |
|---|---|---|
| Alcohol (ethanol) | 7 | beer, wine, spirits |
| Organic acids | 3 | fruit, vinegar, fermented dairy |
| Sugar alcohols (polyols) | 2.4 | "sugar-free" candy and gum |
| Dietary fibre | 2 | vegetables, grains, legumes (EU rules) |
| Erythritol | 0 | sweeteners |
That's why sugar-free candy still carries calories, as polyols give 2.4 kcal per gram while the fat in the chocolate is still 9. And it's why beer adds up so easily, since a gram of alcohol is almost twice as "expensive" as a gram of sugar.
How to check a label in 10 seconds
Multiply the protein and carbohydrate by 4, the fat by 9 and add them up, and the result should match the calories on the pack to within 5-10%. Take the buckwheat in our catalog, which has 4.2 g of protein, 1.1 g of fat and 21.3 g of carbohydrate per 100 g:
4.2 × 4 + 1.1 × 9 + 21.3 × 4 = 16.8 + 9.9 + 85.2 = 112 kcal. The catalog says 110, so it matches.
When the gap is more than 15-20%, the manufacturer has usually taken fibre out of the carbohydrate and counted it separately, or the product contains sugar alcohols or alcohol. And sometimes the label is simply wrong, which happens more often than you'd like.
Why protein is "cheaper" for the body
Digesting and absorbing food also costs energy, and the cost depends on the nutrient. This is called the thermic effect of food:
- protein: 20-30% of its calories go on digestion;
- carbohydrate: 5-10%;
- fat: 0-3%.
Out of 100 kcal of protein the body keeps 70-80, out of 100 kcal of fat almost all of it. This is one reason why a diet with enough protein makes weight loss easier: food is more filling, and the "net" calories come out slightly lower. How much protein you need is covered in How much protein you need a day.
How to turn a calorie target into grams of macros
Say your target is 1,800 kcal and you want 30% of calories from protein, 30% from fat and 40% from carbohydrate.
- Protein: 1,800 × 0.30 = 540 kcal, divided by 4 = 135 g.
- Fat: 1,800 × 0.30 = 540 kcal, divided by 9 = 60 g.
- Carbohydrate: 1,800 × 0.40 = 720 kcal, divided by 4 = 180 g.
To skip the arithmetic, use the macro calculator: it turns your target into grams for your goal.
Where this comes in handy
- Oil in the pan. A tablespoon of vegetable oil is 15 g of fat, which is 135 kcal. People often forget it, although it can be half the calories of the dish.
- A protein shake. A 30 g scoop with 24 g of protein gives about 100-120 kcal, even if it says "no carbs".
- "No-carb" diets. Remove 100 g of carbohydrate (400 kcal) but add 50 g of fat (450 kcal), and you have not created a deficit at all.
In MyFoodMate AI all of this is calculated for you: the photo breakdown shows grams of protein, fat and carbohydrate in the dish, and the diary shows how much is left of each for the day.
We check blog materials against current WHO recommendations.
