Net Carbs Calculator: How to Calculate Net Carbs
Net carbs = total carbohydrate − fiber. Type the numbers from a Nutrition Facts label below. Net carbs is not an FDA-defined term, so we always show total carbs too.
Calculate
Your care team may count carbohydrate differently. Information only.
How it works
- Read the label. Find “Total Carbohydrate” and “Dietary Fiber” for one serving.
- Enter both numbers. Change “servings eaten” if you ate more or less than one.
- See the result. Net carbs are total carbohydrate minus fiber, never below zero.
The formula
Net carbs (g) = total carbohydrate (g) − dietary fiber (g)
Both numbers are in the “Total Carbohydrate” section of the FDA Nutrition Facts label.
For example, a granola bar with 24 g total carbohydrate and 3 g fiber has 21 g net carbs. Two bars have 42 g.
Why “net carbs” is not an official number
The FDA’s Nutrition Facts label lists total carbohydrate, with dietary fiber, total sugars and added sugars underneath. It does not list “net” or “impact” carbs. Those terms come from food marketing, and different brands calculate them differently. When a package says “2 g net carbs”, it is the manufacturer’s math, and it may subtract sugar alcohols or other ingredients, too.
That is why this page, and the rest of this site, shows total carbs first. If your care team teaches carbohydrate counting, ask which number they want you to track. Many count total carbohydrate. Others subtract fiber when a serving has 5 g or more. Neither is wrong, but you should use the same method every time, so your records and readings compare fairly.
What about fiber and sugar alcohols?
Fiber is carbohydrate your body does not break down into glucose in the usual way, which is why some people subtract it. The effect depends on the type of fiber, though, and some products add isolated fibers that behave differently.
Sugar alcohols are partly absorbed, to very different degrees. Erythritol has little effect on glucose in most people, while maltitol can raise it noticeably. They can also cause gas and loose stools. Because of that range, we do not subtract them in the main result. If you enter a number, the calculator shows a second line with them subtracted, so you can compare, and we suggest using that only if your care team tells you to.
Net carbs in the meal planner
The meal planner and carb counter show total carbs, fiber and net carbs (total minus fiber) for every food, so you can use whichever number your care team prefers.
Frequently asked questions
How do you calculate net carbs?
Subtract dietary fiber (in grams) from total carbohydrate (in grams) on the Nutrition Facts label. For example, 30 g total carbohydrate and 5 g fiber is 25 g net carbs.
Is “net carbs” an official term?
No. The FDA does not define “net carbs” or “impact carbs”. Labels that use them are the manufacturer’s own calculation, so check the actual Nutrition Facts panel.
Should I subtract sugar alcohols too?
Only if your care team tells you to. Sugar alcohols such as erythritol, xylitol, sorbitol and maltitol are partly absorbed to different degrees, and some, like maltitol, can raise glucose noticeably. Because the effect varies, our result subtracts fiber only, and shows the sugar alcohol version separately.
Do net carbs matter for insulin or medicine doses?
This tool never calculates a dose. If your care team uses a carbohydrate count for your treatment, ask them which number they want you to use.
Why does the meal planner show net carbs?
Because many people ask for it. The planner shows total carbs, fiber and net carbs side by side so you can use whichever your care team uses.
Information only, not medical advice. Your care team may set different targets for you, and only a lab test ordered by a clinician can diagnose diabetes or prediabetes. See our medical disclaimer.
Sources
- FDA: How to understand and use the Nutrition Facts label
- CDC: Diabetes Meal Planning (carbohydrate counting)
- USDA FoodData Central
Last reviewed: by the Diabetes Blogs editorial team. Information only, not medical advice.
