How many calories in 1 gram of carbs? 4 kcal.
Short answer: 1 g of carbohydrates ≈ 4 kcal. Same as protein, but for a different chemical reason. White sugar, honey, rice, oats, banana, pasta, bread: every one of them is 4 kcal per gram of carbs. This applies to simple carbs (glucose, fructose, sucrose) and complex carbs (starch). The difference between a "bad sugar" and a "good carb" lies in absorption speed and glycemic load, not in calories per gram.
There are two exceptions: fiber and sugar alcohols (xylitol, erythritol). More on those below.
Energy value of carbs: the numbers
| Carbohydrate source | Energy from carbs (kcal/g) | Total energy (kcal/100g) | Carbs (g/100g) |
|---|---|---|---|
| White sugar (sucrose) | 4.0 | 387 | 99.8 |
| White rice, cooked | 4.0 | 130 | 28 |
| Oats, dry | 4.0 | 379 | 67 |
| Banana | 4.0 | 89 | 22.8 |
| Wheat bread | 4.0 | 265 | 49 |
| Honey | 4.0 | 304 | 82.4 |
- Confidence: high. The 4 kcal/g coefficient is the Atwater convention. Real energy density of carbs in a calorimeter is 3.79–4.16 kcal/g (from starch to glucose). Digestibility: simple sugars and sucrose ~98%, cooked starch ~95%, raw starch (green bananas, uncooked rice) ~70–80%. USDA, EFSA, FAO/WHO and major nutrition agencies use the unified 4 kcal/g.
Why do simple sugars and oats have the same kcal/g?
Because all digestible carbs ultimately become the same monosaccharides: glucose, fructose, and galactose. Starch from oats is broken down by amylase into glucose. Sucrose (white sugar) is broken down by sucrase into glucose + fructose. Your body burns these monosaccharides and gets ~3.7–4.2 kcal/g of energy, regardless of source.
What does differ:
- Absorption speed. White sugar raises blood glucose in 15 min. Oats take 60–90 min. Practically relevant for insulin and hunger, not for calories.
- Co-nutrients. Oats have magnesium, fiber, B vitamins. White sugar has none. That's a health argument, not a calorie one.
- Satiety. A meal rich in starch + fiber digests longer, so it satisfies longer. From a "how many kcal did I eat" perspective, no difference.
Carb TEF. Carb digestion costs ~5–10% of its energy. From 100 kcal of carbs you actually use ~92 kcal. For comparison: protein ~75, fat ~97. Middle of the pack.
Exceptions: fiber and sugar alcohols
Not every "carbohydrate" counts as 4 kcal/g. EU product labels distinguish several categories:
| Category | kcal/g | Examples |
|---|---|---|
| Simple sugars | 4.0 | glucose, fructose, sucrose, honey |
| Starch | 4.0 | flour, rice, potatoes, oats |
| Soluble fiber | ~2.0 | inulin, beta-glucan (oats), pectins |
| Insoluble fiber | ~0 | cellulose, wheat bran |
| Sugar alcohols (polyols) | 0.2–2.4 | erythritol (~0.2), xylitol (~2.4), maltitol (~2.1) |
| Non-caloric sweeteners | 0 | sucralose, aspartame, stevia |
In practice: the label shows "Carbohydrates 30g, of which sugars 12g, fiber 5g". You compute 30 × 4 + 5 × 2 minus insoluble fiber = ~130 kcal from carbs. BiteNote does this arithmetic for you in the chat, in seconds.
Sample log in BiteNote
📸 → BiteNote: oatmeal with banana and milk, ~340 kcal (315–365). Carbs ~52g = 208 kcal from carbs. Confidence: high.
An average banana (~120g) is ~108 kcal, of which ~88 kcal comes from carbs alone.
📸 → BiteNote: banana, medium, ~108 kcal (102–115). Carbs ~22g = 88 kcal from carbs. Confidence: high.
FAQ
Do simple sugars have the same calories as complex carbs?
Yes, both 4 kcal/g. Simple sugars (glucose, fructose) and complex (starch) differ in absorption speed and insulin impact, not in calories per gram. White sugar isn't "more calories" than oats, it's faster calories.
Is fiber also 4 kcal/g?
No. Soluble fiber (inulin, beta-glucan, pectins) is ~2 kcal/g. Insoluble fiber (cellulose, lignin) is practically 0 kcal/g, because it's not digested. EU labels include fiber in "total carbohydrates," but its energy contribution is lower than the rest.
Does fructose make you gain more weight than glucose, given both are 4 kcal/g?
Per gram, identically. Fructose has a lower glycemic index (it doesn't spike insulin like glucose does), but it's metabolized mainly in the liver. Excess fructose from sweetened drinks may strain the liver and contribute to abdominal fat. Fructose from fruit (with fiber and water) doesn't show this effect.
Is keto / low-carb dieting "fewer calories"?
Not necessarily. A ketogenic diet limits carbs to ~5–10% of energy, but fat has 9 kcal/g vs 4 kcal/g for carbs. You can do keto on 2500 kcal and low-fat on 1500 kcal. Daily calorie balance is what counts, not the macro percentage.
Do sugar alcohols (xylitol, erythritol) count as carbs?
Yes, but with different coefficients. Erythritol ~0.2 kcal/g (labeled as 0 in the EU), xylitol ~2.4 kcal/g, maltitol ~2.1 kcal/g. EU product labels must distinguish them. BiteNote recognizes them if you give it a product name from the OpenFoodFacts database.
Related
- Atwater factors: full table
- How many calories in 1 g of protein?
- How many calories in 1 g of fat?
- How many calories in 1 g of alcohol?
- Oats vs rice: carb comparison
Sources
- USDA FoodData Central: Sugars, granulated #169655: 387 kcal, 99.8 g carbs per 100 g
- USDA FoodData Central: Bananas, raw #173944: 89 kcal, 22.8 g carbs per 100 g
- USDA FoodData Central: Rice, white, long-grain, regular, cooked #168878
- FAO/WHO: Food energy: methods of analysis and conversion factors (Report 77, 2003), section 3.4 on fiber and sugar alcohols
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