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Net Carbs Calculator

Find the net carbs in a food from its nutrition label. Fiber and sugar alcohols are taken away from total carbohydrate, for one serving or several.

Level: Grade 5

  • Common Core standard 5.NBT.B.7Add, subtract, multiply, and divide decimals to hundredths, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.
Printable worksheet

Net Carbs Calculator

Know the answer you need? Pick an input to work backward.

Inputs
Nutrition label

Enter 0 if the label doesn't list them.

Only needed for the half method; check the ingredients list.

Sugar alcohols

Result

Net carbs

10 g

1 serving with 24 g of carbohydrate each come to about 10 g of net carbs.

Net carbs per serving
10 g
Subtracted per serving
14 gFiber plus sugar alcohols
Total carbohydrate eaten
24 g

See the step-by-step solution ↓

Step-by-step solution

  1. Take the fiber and sugar alcohols away from total carbohydrate, since your body digests little of them. This gives net carbs per serving

    24−8−6=10 g

Test yourself

20 quick questions built from this calculator's formula: work out results, predict what happens when an input changes, and work backward from an answer. Every answer comes with the working.

What this calculator does

Find the net carbs in a food, straight from the numbers on its nutrition label. Net carbs are the carbohydrates left after taking away the parts your body digests little or not at all. Those parts are dietary fiber and, usually, sugar alcohols such as erythritol, xylitol and maltitol.

People on low-carbohydrate eating plans often count net carbs instead of total carbohydrate. This calculator does the subtraction from the label figures. Then it scales the result to the number of servings you eat.

Labels differ by country. In the US and Canada, the total carbohydrate line includes fiber, so fiber has to be subtracted. In the EU, UK, Australia and New Zealand, fiber is listed on its own line. The carbohydrate line already leaves it out, so subtracting it again would count it twice. Choose your label style and the calculator handles the difference for you.

Where it's used

Why this math matters outside the classroom:

  • Label reading. A shopper finds a cereal with 31.5 g of carbs and 9.5 g of fiber has 31.5 − 9.5 = 22 g of net carbs.
  • Meal tracking. Someone counting carbs eats 1.5 servings of crackers at 12.4 g net carbs each, which is 18.6 g.
  • Decimal subtraction. Students subtract 4.5 g and 2.25 g from 20 g to get 13.25 g, practising decimals to hundredths.
  • Comparing products. Shoppers compare two protein bars, one with 6 g and one with 14 g of net carbs, before buying.
  • Recipe planning. A home cook adds up net carbs for each ingredient, then divides by servings to label a sugar-free dessert.

Grade level and standards: Grade 5; Common Core State Standards for Mathematics 5.NBT.B.7. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.

How to use it

  1. Choose the style of nutrition label you're reading.
  2. Enter total carbohydrate, dietary fiber (US and Canada) and sugar alcohols per serving, in grams.
  3. Choose whether to subtract sugar alcohols in full or by half. For the half method, enter how much of them is erythritol, if the label or ingredients say.
  4. Enter the number of servings you eat, then read your net carbs.

What the inputs mean

Nutrition label
Check the label wording. A US label says Total Carbohydrate, with Dietary Fiber indented below it. An EU or UK label lists Carbohydrate and Fibre as separate lines.
Sugar alcohols (polyols) per serving
Listed as sugar alcohols or polyols, often only on products that claim to be sugar-free. Ingredients ending in -itol (sorbitol, maltitol, xylitol, erythritol) are sugar alcohols.
Of which erythritol
Only needed for the half method; check the ingredients list.
Sugar alcohols
Subtracting all sugar alcohols is the most common method. Some people subtract only half of the sugar alcohols other than erythritol, because the body partly absorbs those. Erythritol is mostly not absorbed, so it's subtracted in full either way.
Servings eaten
Decimals work: half a bar is 0.5 servings.

Formula and method

US or Canada: net carbs = total carbohydrate − fiber − sugar alcohols
EU, UK, Australia or NZ: net carbs = carbohydrate − sugar alcohols
half method: sugar alcohols subtracted = (sugar alcohols − erythritol) ÷ 2 + erythritol
net carbs eaten = net carbs per serving × servings

On a US label, total carbohydrate counts starch, sugars, fiber and sugar alcohols together. Taking away fiber and sugar alcohols leaves mostly the starch and sugars your body digests and absorbs. That's what net carbs try to capture.

Fiber and sugar alcohols are part of the total, so they can't add up to more than it. If they do, a figure has been misread. The calculator tells you so, rather than showing a negative number.

Worked example

A US snack bar label lists 24 g total carbohydrate, 8 g dietary fiber and 6 g sugar alcohols per bar. You eat one bar.

  1. Net carbs per serving: 24 − 8 − 6 = 10 g.
  2. With the half method and no erythritol, you'd subtract 6 ÷ 2 = 3 g of sugar alcohols instead: 24 − 8 − 3 = 13 g.
  3. One bar eaten: 10 g of net carbs with the usual method.

Result: The bar has about 10 g of net carbs (13 g if you count half of its sugar alcohols).

Understanding the result

Net carbs are an estimate of the carbohydrate you digest, not a lab measurement. Two people can count the same food differently, depending on how they treat sugar alcohols.

If you track total carbohydrate for a health reason, follow the method your doctor or dietitian uses. This calculator only does the arithmetic.

Assumptions and limitations

  • Label values are per serving and accurate.
  • On US and Canadian labels, fiber and sugar alcohols are included in total carbohydrate.
  • Erythritol, when you enter it, is part of the sugar alcohol figure.
  • Net carbs isn't a term defined by US food labeling rules. Package claims of net or impact carbs may use other methods.
  • People treat allulose (a rare sugar) and some fibers added to processed foods in different ways. This calculator subtracts only what you enter as fiber or sugar alcohols.
  • It's a tool for label arithmetic, not dietary or medical advice.

Frequently asked questions

How do you calculate net carbs?

On a US or Canadian label, subtract dietary fiber and sugar alcohols from total carbohydrate. 30 g total with 5 g fiber and 4 g sugar alcohols is 30 − 5 − 4 = 21 g net carbs.

Should I subtract all sugar alcohols?

Most people do. Some subtract only half of sugar alcohols such as maltitol and sorbitol, which the body partly absorbs. They still subtract erythritol in full. The calculator offers both methods.

Why are net carbs lower on US labels than the total?

Because US total carbohydrate includes fiber. European labels already leave fiber out of the carbohydrate line. So their carbohydrate figure is closer to net carbs to begin with.

Do net carbs appear on the nutrition label?

Not on the official US Nutrition Facts panel. When a package shows net carbs somewhere else, it's the maker's own calculation, which may differ from yours.

How this calculator is checked

Method: Common net-carbohydrate arithmetic (total carbohydrate minus dietary fiber and sugar alcohols), with the half-sugar-alcohol variant; label conventions of US/Canadian (fiber within total carbohydrate) and EU/UK/Australian (fiber listed separately) nutrition labels. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.

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