Whole carbohydrates per 100 grams — also called total carbs per 100g — is the clearest way to compare how carbohydrate-dense different foods are. Label serving sizes vary wildly (a slice, a cup, a handful), so a food with 20 g of carbs per serving may sound modest until you check what serving the label assumes. This calculator takes the total carbohydrate amount from any nutrition label, along with the serving weight, and standardizes it to a per-100g basis.
You can optionally enter dietary fiber and sugar alcohols to see net carbs per 100g as well. That extra view is helpful for low-carb meal planning, blood sugar management, and comparing whole foods like grains, legumes, fruit, and starchy vegetables. The tool handles grams, ounces, or kilograms for serving weight, and it works with any label — fresh produce entries, packaged foods, or recipe estimates. Just type in the numbers you see on the label, and the result will be ready in seconds.
🧮 Whole Carbs Per 100g Calculator
Standardize any food label to grams of carbs per 100g.
How to Use This Tool
Using this calculator takes less than a minute. First, find the nutrition facts panel on your food package, or look up the serving data for a fresh food from a trusted database such as the USDA FoodData Central. Note two numbers: the serving size in grams and the Total Carbohydrate line in grams. Enter the serving weight into the first field and the carbohydrate amount into the second field. If the serving size is listed in ounces or kilograms, choose that unit from the dropdown and the calculator will convert it to grams automatically.
For a more complete picture, add the dietary fiber and, if present, sugar alcohols from the same label. The net-carbs result uses the familiar formula: total carbs minus fiber minus sugar alcohols. When you press Calculate, the tool reports whole carbs per 100 g and, if enabled, net carbs per 100 g. You can use the quick-fill buttons for common foods to test how the inputs work.
Formula Explained
The calculation is a simple proportion. If a food has C grams of total carbohydrate in a serving that weighs S grams, then the same food will have C ÷ S grams of carbohydrate in every 1 g, and therefore:
Whole carbs per 100 g = (Total carbs per serving ÷ Serving weight in g) × 100
For net carbs, you subtract dietary fiber and sugar alcohols from the total before applying the same proportion:
Net carbs per 100 g = ((Total carbs − Fiber − Sugar alcohols) ÷ Serving weight in g) × 100
This assumes the serving weight represents the entire edible portion you are measuring. Cooked and raw foods differ in water content, so a food's carbohydrate density can change dramatically after cooking; always use the state of the food that matches the label.
Worked Examples
Example 1 — Cooked quinoa. A label says 1 serving is 93 g (about ½ cup) and contains 21.3 g total carbs and 2.8 g fiber. Whole carbs per 100 g = (21.3 ÷ 93) × 100 = 22.9 g/100g. Net carbs per 100 g = ((21.3 − 2.8) ÷ 93) × 100 = 19.9 g/100g.
Example 2 — Nutrition bar. A bar weighs 40 g and contains 24 g total carbs, 2 g fiber, and 5 g sugar alcohols. Whole carbs per 100 g = (24 ÷ 40) × 100 = 60 g/100g. Net carbs per 100 g = ((24 − 2 − 5) ÷ 40) × 100 = 42.5 g/100g. This shows how much a small serving can obscure a high carb density.
Per-100g comparison is especially useful when two foods have very different serving sizes. A food with 10 g carbs per 30 g serving and a food with 25 g carbs per 150 g serving both end up around 16–17 g per 100 g once standardized.
Tips & Best Practices
- Use grams, not volume. A cup of chopped fruit and a cup of whole berries weigh very differently; grams are the reliable baseline.
- For fresh produce, check whether the database entry is for the raw or cooked form. A cup of cooked rice has about 200 g; raw rice has about 185 g but absorbs water when cooked, changing carb density per volume.
- If the label lists sugar alcohols, subtract them if you are counting net carbs for a low-carb plan. Note that some experts subtract only half for certain sugar alcohols like erythritol, so the conventional full subtraction is a simplification.
- Use the result to build flexible comparisons: a starchy vegetable with 20 g whole carbs per 100 g is not the same as a leafy green with 3 g per 100 g, even if your serving sizes look similar on the plate.
Limitations & Precision Notes
This calculator is only as accurate as the label or database values you enter. Nutrition labels in the United States allow total carbohydrate declarations to be rounded to the nearest gram, so a label showing 31 g could represent anywhere from 30.5 to 31.5 g. Fiber rounding is even looser, which can shift net-carb estimates by 1–2 g per 100 g depending on the food. The USDA FoodData Central provides more precise values for many whole foods and is a good cross-check.
For certain very high-fiber foods, the computed net carbs can be negative. In practice, digestible carbs cannot be below zero, so this tool reports negative net values as 0. Also, the sugar alcohol subtraction treats all sugar alcohols equally; some have a lower glycemic impact than others. If you are following a medically prescribed carbohydrate count for diabetes, always confirm with your healthcare provider before relying on net-carb calculations.
Frequently Asked Questions
Is whole carbs the same as total carbs? In the context of this tool, yes. Whole carbs refers to the complete carbohydrate line on a nutrition label, including fiber. Net carbs is the smaller figure you get after removing fiber and sugar alcohols.
Why compare per 100 g instead of per serving? Serving sizes are chosen by food manufacturers and can be unreasonably small or accidentally large. Per-100g is a neutral standard used by nutrition databases worldwide, so it lets you compare apples to oranges — literally — without serving-size bias.
Can I use this for foods cooked from dry ingredients? Yes, but be consistent. If you cook 50 g of dry oats and the cooked porridge weighs 220 g, enter the cooked weight and the carb amount from the dry ingredient (the carbs don't change during cooking). The per-100g result then reflects the cooked food as eaten.
Does fiber really count as a carb? It does on a nutrition label, but your body doesn't digest most fiber the same way. That's why net-carbs methods subtract it. For general meal planning, both whole carbs and net carbs are useful — they answer different questions.