1. Select the exact state
Match raw vs cooked, drained vs undrained, enriched vs unenriched, and branded vs generic. Food state is part of the record—not a footnote.
Open method · Reusable output · No sign-up
Net Carb Calculator
Turn label or USDA values into a serving-level net-carb estimate—and see every assumption behind the number.
Net carbs = total carbohydrate − fiber − selected polyol adjustment
Calculator
Enter values for one serving
There is no single subtraction rule that fits every sugar alcohol or every person. The default makes no polyol deduction. Compare the product label and discuss condition-specific tracking with a qualified clinician.
Estimated result
15.0g
net carbs for 1 serving
(20.0 − 5.0 − 0.0) × 1 = 15.0g
Transparent methodology
How CheckTheCarbs builds a number
2. Normalize the serving
When source data are per 100g, each nutrient is multiplied by serving grams ÷ 100. Household measures always show their gram assumption.
3. Calculate, then round
Net carbs are calculated from unrounded source values. Display rounding happens last, usually to one decimal place.
source total carbs per 100g × (serving grams ÷ 100) = serving total carbs
source fiber per 100g × (serving grams ÷ 100) = serving fiber
serving total carbs − serving fiber = serving net carbs
source fiber per 100g × (serving grams ÷ 100) = serving fiber
serving total carbs − serving fiber = serving net carbs
Source hierarchy
- USDA FoodData Central Foundation, SR Legacy, or FNDDS records for generic foods.
- Current manufacturer Nutrition Facts for branded foods when the product can be identified precisely.
- Documented derivation only when a serving must be scaled from a source record.
USDA FoodData Central publishes food composition data and requests attribution. Open FoodData Central. The FDA’s label guidance explains that Total Carbohydrate includes fiber, sugars, and sugar alcohols; serving amounts on a label refer to the stated serving. Read FDA label guidance.
Correction policy
Corrections are evaluated against the exact food state, serving weight, source record, and publication date. Accepted corrections update the visible table, structured data, source note, and modification date together.
A correction should identify the page URL, disputed value, exact product or food state, serving weight, and a primary-source link or label image. Differences caused only by rounding or a different serving are documented rather than silently overwritten.
No pay-to-change policy: sponsorship, affiliate relationships, or outreach do not determine nutrition values or source selection.
Downloadable and embeddable outputs
The CSV button exports the entered values, selected adjustment, formula, result, page URL, and calculation date. The embed button copies a static HTML citation block so editors can quote the result without running third-party code.
The generated embed links back to this methodology page for provenance. Publishers may edit the styling but should preserve the food state, serving size, calculation date, and source link.
Calculator questions
What is the basic net-carb formula?
For foods without sugar alcohols: total carbohydrate minus dietary fiber. The calculator prevents a negative displayed result.
Are net carbs an FDA-defined label nutrient?
No. U.S. labels list Total Carbohydrate and Dietary Fiber. Net carbs are a consumer tracking convention calculated from those values.
Why is sugar-alcohol subtraction optional?
Sugar alcohols differ in absorption and labeling, and a single universal deduction can mislead. This tool defaults to no deduction and makes the selected assumption visible.
Can I cite or embed the result?
Yes. Use the static embed output and keep the serving, food state, date, and methodology link with the number.