Quick answer
Net carbs = total carbohydrate − fibre − sugar alcohols. A food with 25 g total carbohydrate and 8 g fibre has 17 g net carbs.
Enter total carbohydrate, fibre and optionally sugar alcohols. The calculator returns net carbs.
Related tools: Calorie Calculator: Daily calories to maintain, lose or gain weight. BMR Calculator: Estimate basal metabolic rate with the Mifflin–St Jeor and revised Harris–Benedict equations. TDEE Calculator: Total daily energy expenditure from BMR and activity level.
How to use the Net Carb Calculator
- Enter total carbohydrate (g) (0 or more).
- Enter dietary fiber (g) (0 or more).
- Optionally, enter sugar alcohols to subtract (g) (0 or more).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Total carbohydrate | A number, in g | ≥ 0 |
| Dietary fiber | A number, in g | ≥ 0 |
| Sugar alcohols to subtract (optional) | A number, in g | ≥ 0 |
Formula and method
Formula
net carbs = total carbohydrate − fiber − sugar alcohols
IEEE-754 double precision; shown to the decimals indicated.
Which sugar alcohols to subtract is a choice; enter only the amount you want removed. Informational estimate, not medical advice. Talk to a qualified health professional about your own situation.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Total carbohydrate = 25; Dietary fiber = 8.
| Result | Value |
|---|---|
| Net carbs | 17 g |
| Subtracted | 8 g |
Example 2
Inputs: Total carbohydrate = 30; Dietary fiber = 12; Sugar alcohols to subtract = 6.
| Result | Value |
|---|---|
| Net carbs | 12 g |
| Subtracted | 18 g |
Example 3
Inputs: Total carbohydrate = 10; Dietary fiber = 2; Sugar alcohols to subtract = 0.
| Result | Value |
|---|---|
| Net carbs | 8 g |
| Subtracted | 2 g |
The first line is the headline result (net carbs). Below it the net Carb Calculator lists subtracted, which describe the same case from other angles. IEEE-754 double precision; shown to the decimals indicated.
Why subtract fibre
Fibre is not digested into glucose, so it's often subtracted when counting carbs for low-carb diets. Some sugar alcohols are only partly absorbed, but different ones raise blood sugar differently, and regulators don't define 'net carbs'.
Cautions
The result can't be negative. People with diabetes should follow their care team's guidance, as total carbohydrate often matters for insulin dosing.
How the result changes with total carbohydrate
Holding every other input at the first worked example, this table changes only total carbohydrate. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Total carbohydrate | Net carbs | Subtracted |
|---|---|---|
| 12.5 | 4.5 g | 8 g |
| 25 | 17 g | 8 g |
| 50 | 42 g | 8 g |
| 100 | 92 g | 8 g |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Dietary fiber: entering "12" shows "Fiber and sugar alcohols cannot exceed total carbohydrate." beside that field and no result.
- Total carbohydrate: left empty shows "Enter total carbohydrate." beside that field and no result.
Choosing between the Net Carb Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Calorie Calculator](/health/calorie-calculator/) | units, sex and weight | Maintenance calories |
| [BMR Calculator](/health/bmr-calculator/) | units, sex and weight | Basal metabolic rate |
| [TDEE Calculator](/health/tdee-calculator/) | units, sex and weight | Total daily energy expenditure |
| [Protein Calculator](/health/protein-calculator/) | units, body weight and profile | Protein per day |
| [Macro Calculator](/health/macro-calculator/) | daily calories, carbohydrate and protein | Carbohydrate |
Background: nutrition estimates
Nutrition calculators estimate: they use population-average equations and food tables, and different tables give different numbers for the same food. Certain medical conditions change energy needs in ways basic formulas cannot see, and only laboratory analysis gives exact nutrient values.
Use the result as a starting point, track what actually happens over a few weeks and adjust; ask a qualified professional about medical or clinical decisions.
Assumptions and limitations
- Result cannot be negative
- Not a diagnosis
This calculator gives general information based on published formulas. It is not medical advice, and it cannot account for your health history. Talk to a qualified clinician about decisions that affect your health.
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for dietary fiber and total carbohydrate to confirm this.
Frequently asked questions
Is net carbs an official term?
No, it's a common convention.
Do all sugar alcohols subtract fully?
No, erythritol does more than maltitol.
What is the daily net carb limit on keto?
Commonly 20 to 50 g.
What does the Net Carb Calculator calculate?
Net carbohydrates after subtracting fiber and sugar alcohols. It returns Net carbs and Subtracted.
What formula does the Net Carb Calculator use?
net carbs = total carbohydrate − fiber − sugar alcohols. Which sugar alcohols to subtract is a choice; enter only the amount you want removed.
What do I need to enter in the net Carb Calculator?
You enter Total carbohydrate (g) and Dietary fiber (g). Optional: Sugar alcohols to subtract (g).
How is the result rounded or limited?
IEEE-754 double precision; shown to the decimals indicated. Result cannot be negative.
What are the limits of this calculator?
Result cannot be negative. Not a diagnosis.
What is an example of a net Carb result?
With total carbohydrate 25 and dietary fiber 8, the net carbs is 17 g.
Where does the method come from?
The method follows: Common definition used on this page. No single authoritative standard defines it, so the exact formula is stated in the formula section above: no regulatory definition of net carbs in the US.
Can I rely on this calculator for a decision?
This calculator gives general information based on published formulas. It is not medical advice, and it cannot account for your health history. Talk to a qualified clinician about decisions that affect your health. For this calculator in particular: Result cannot be negative.
Related calculators
- Calorie Calculator — Daily calories to maintain, lose or gain weight.
- BMR Calculator — Estimate basal metabolic rate with the Mifflin–St Jeor and revised Harris–Benedict equations.
- TDEE Calculator — Total daily energy expenditure from BMR and activity level.
- Protein Calculator — Daily protein target by body weight and activity.
- Macro Calculator — Split daily calories into grams of carbohydrate, protein and fat.
- Calories Burned Calculator — Estimate calories burned from activity, body weight and time using MET values.
Sources
- Common definition used on this page. No single authoritative standard defines it, so the exact formula is stated in the formula section above: no regulatory definition of net carbs in the US
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.