FREE KETO TOOL

NET CARBS CALCULATOR

Turn the numbers on any nutrition label into net carbs per serving. Subtract fiber and sugar alcohols, and see exactly how the math works.

g
g
g
Net carbs per serving
12gper serving
Net carbs (whole recipe)12g
How we got there

20g carbs − 8g fiber − 0g sugar alcohol = 12g net carbs

12g ÷ 1 serving = 12g per serving

Erythritol and allulose pass through undigested, so they subtract fully. Maltitol and most other polyols are partly absorbed, so only half comes off.

Total carbs vs net carbs

On a US nutrition label, total carbohydrates include every carb in the food, whether or not your body can use it for energy. That total lumps together starches and sugars, which raise blood sugar, along with fiber and sugar alcohols, which mostly do not.

Net carbs are the carbs that actually affect your blood sugar and your ketosis. You get them by subtracting fiber and eligible sugar alcohols from the total. That is why a high-fiber wrap or a keto dessert can look carb-heavy on the label yet still fit an entire day of keto eating.

How the net carbs formula works

The calculator uses one simple equation:

Net carbs = total carbs − fiber − sugar alcohols

Fiber comes off in full. Fiber is a carbohydrate your body cannot digest, so it passes through without spiking blood sugar. There are two broad types: insoluble fiber, which adds bulk and keeps digestion moving, and soluble fiber, which forms a gel and feeds your gut bacteria. Neither is used for quick energy, so both are subtracted.

The sugar alcohol nuance

Sugar alcohols are where people get tripped up, because they are not all equal. The calculator handles the difference for you:

  • Erythritol and allulose are almost entirely unabsorbed and have a near-zero effect on blood sugar, so you subtract them fully. If you want the detail, see our guide on allulose on keto.
  • Maltitol is a different story. It is partly digested and does raise blood sugar, so only about half of it should be subtracted.
  • Other polyols like sorbitol and xylitol fall in between, so subtracting half is the safe default.

Label-reading gotchas

A few traps to watch for. First, European labels already exclude fiber from the carb figure, so the "carbohydrate" line is closer to net carbs already; do not double-subtract. Second, serving sizes are easy to miss. If a package holds four servings and you eat the whole thing, multiply accordingly, or enter the whole-package numbers and set servings to one in the tool. Third, rounding rules let manufacturers list "0g" carbs for anything under half a gram per serving, which quietly adds up across a day.

When you are ready to build meals, pair this tool with our keto food list so you know which whole foods are naturally low in net carbs. And to work out your daily carb ceiling in the first place, run the numbers through our keto calculator.

Frequently Asked Questions

How do you calculate net carbs?

Net carbs equal total carbohydrates minus dietary fiber minus sugar alcohols. Fiber and most sugar alcohols are not fully digested, so they have little effect on blood sugar. For example, a bar with 20g total carbs, 8g fiber, and 6g erythritol has 6g net carbs.

Do you subtract fiber on keto?

Yes, most keto eaters subtract fiber to get net carbs. Fiber is a carbohydrate your body cannot break down for energy, so it does not raise blood sugar or stop ketosis. Subtract all of the fiber listed on a US nutrition label. In Europe fiber is already excluded from the carb count, so no subtraction is needed there.

Do sugar alcohols count as carbs on keto?

It depends on the sugar alcohol. Erythritol and allulose pass through the body almost entirely undigested, so you subtract them fully. Maltitol is partly absorbed and does raise blood sugar, so subtract only half. When in doubt with an unknown polyol, subtract half to stay safe.

Is 50g net carbs still keto?

For many people, yes. The common keto range is 20 to 50 grams of net carbs per day. Lean, active, and fat-adapted people can often stay in ketosis near 50 grams, while beginners and insulin-resistant people usually need to stay closer to 20 to 25 grams to get into ketosis.

Why do total carbs and net carbs differ?

On a US label, total carbohydrates include fiber and sugar alcohols. Net carbs strip those out because they have little impact on blood sugar. That is why a high-fiber food can look carb-heavy on the label yet fit easily into a keto day once you calculate net carbs.