Keto Net Carb Calculator
Snap a nutrition label, scan a barcode, or type the numbers. This free keto net carb calculator counts fiber and sugar alcohols the right way, so a “2 g net carbs” claim cannot fool you.
Keto Net Carb Calculator
Take a photo of the Nutrition Facts panel. Include the ingredient list if you can — that is where hidden sweeteners show up.
- Good light, phone held steady, label filling most of the screen.
- Your photo is used only to read the label. LowCarb Avenue does not save it.
Scan the barcode on the package. We look it up in Open Food Facts, a free public food database.
or type the number under the barcode
Type the numbers from the label. Your answer updates as you type.
Use it like an app: tap Share then Add to Home Screen.
How we decide the color
- Clean Keto: 5 g net carbs or less per serving, with no maltitol-type sugar alcohols or fast sugars flagged.
- Use Caution: more than 5 g, or contains partly digested sugar alcohols, IMO, maltodextrin, dextrose or syrups.
- High Blood Sugar Impact: more than 10 g, or 6 g or more with maltitol-type sugar alcohols or IMO.
- These are general rules of thumb, not medical advice. Your own glucose response is the best guide.
Free · No sign-up · For education only, not medical advice. If you take insulin or diabetes medicine, ask your care team before changing your diet.
How the net carb scanner works
Snap or scan
Point your phone at the Nutrition Facts panel and ingredient list, or at the barcode. No app store, no account.
Sweetener check
The calculator reads the ingredients. It tells erythritol and allulose apart from maltitol, sorbitol and other sweeteners that act more like sugar.
True net carbs
You get one clear number per serving, a color rating, and the full math, line by line. Nothing is hidden.
Why the net carbs on the box can be wrong
“Net carbs” is a popular way to count the carbs that actually raise blood sugar. But it is not a term the U.S. Food and Drug Administration (FDA) defines. So each brand can do the math its own way. Here are the four traps we see most often.
1. The maltitol trap
Most brands subtract all sugar alcohols from total carbs. That works for erythritol, which has a glycemic index (GI) of about 0. It does not work for maltitol, which has a GI of about 35 in a major review of the research. Your body digests a good part of it. A bar with 12 g of maltitol can claim 3 g net carbs when the honest number is closer to 9 g.
2. Rounding on the label
Under FDA rules, carbs are rounded to the nearest gram. A line that reads “0 g” can mean up to 0.49 g. “Less than 1 g” can mean almost a full gram. That is tiny for one serving, but it adds up when you eat four or five servings a day.
3. Small serving sizes
Check the serving size before you trust any number. A package may list half a bar, or 2 crackers, as one serving. The calculator lets you set how many servings you will really eat, and it updates the total for you.
4. “Fibers” that act like sugar
Some added fibers are low impact. Others are not. Studies show isomalto-oligosaccharides (IMO), often sold as a fiber syrup, can raise blood sugar much like regular sugar. The calculator flags IMO, maltodextrin, dextrose and sugar syrups so you can decide for yourself.
How this calculator works out net carbs
The formula is simple and the same every time:
True net carbs = total carbs − fiber − erythritol − allulose − (½ Ă— maltitol, sorbitol and other sugar alcohols)
| Ingredient | How we count it | Why |
|---|---|---|
| Dietary fiber | Subtract 100% | Not digested into sugar |
| Erythritol | Subtract 100% | Glycemic index of about 0 |
| Allulose | Subtract 100% | FDA lets brands leave it out of “sugars” because the body does not use it like table sugar |
| Stevia, monk fruit, sucralose | No change | Used in tiny amounts with no meaningful carbs |
| Maltitol, sorbitol, xylitol, isomalt, lactitol | Subtract only 50% | Partly digested; maltitol has the biggest effect |
| IMO, maltodextrin, dextrose, syrups | Counted in full and flagged | Digestible carbs that can raise blood sugar fast |
When a label lumps all sugar alcohols into one line, and the ingredients show maltitol or another partly digested sugar alcohol, we count the whole line at 50%. That keeps the answer on the safe side. The AI only reads the label. The math itself runs in plain code in your browser, so the same numbers always give the same answer.
Want the full explanation? Read our LowCarb Wiki guides: What Are Net Carbs? How to Calculate Them and Sugar Alcohols and Low-Carb Sweeteners.
What the colors mean
- Clean Keto (green): 5 g net carbs or less per serving, with no partly digested sugar alcohols or fast sugars flagged.
- Use Caution (amber): more than 5 g, or it contains maltitol-type sugar alcohols, IMO, maltodextrin, dextrose or syrups.
- High Blood Sugar Impact (red): more than 10 g, or 6 g or more with maltitol or IMO.
These are rules of thumb, not medical advice. People respond differently. If you use a glucose meter or CGM, your own readings are the best guide. If you take insulin or diabetes medicine, talk with your care team before you change how you eat.
Why a physician co-founded bakery built a free tool
LowCarb Avenue is a family-owned artisan bakery in Frederick, Maryland, co-founded by a physician. We bake low carb sourdough, breads and bagels the slow way, with olive oil and clean, non-GMO ingredients. Many of our customers manage diabetes or follow keto. They kept asking us the same question at farmers markets: “Can I trust this label?”
This calculator is our answer. It is free, it works on any product from any brand, and it does not ask for your email. We built it to make label reading easy, not to sell you something.
Frequently asked questions
Is this keto net carb calculator free?
Yes. It is 100% free, with no sign-up and no app store download. It runs in your phone or computer’s web browser.
Do you save my label photos?
No. Your photo is sent securely to an AI service only to read the label, and LowCarb Avenue does not store it. Manual Math never leaves your device.
Why can’t the barcode scanner find my product?
Barcode results come from Open Food Facts, a free public database built by volunteers. Some products are missing or incomplete. If a barcode is not found, snap a photo of the label or use Manual Math.
How do I add the calculator to my home screen?
On iPhone or iPad, open this page in Safari, tap Share, then “Add to Home Screen.” On Android, tap the “Add this calculator to my home screen” button, or use the browser menu and choose “Install app.”
How accurate is the label scanner?
It reads clear, well-lit photos well, but glare or blur can cause mistakes. Always compare the numbers with the package. Tap “Edit numbers” to fix anything in seconds.
Real bread, honest numbers
If you are looking for bread that does not need a calculator to make sense, try our clean-label low carb sourdough and keto bagels, made with real fiber and protein. Shop LowCarb Avenue.
Sources: Livesey G. Health potential of polyols as sugar replacers, Nutrition Research Reviews, 2003 · FDA, Declaration of Allulose on Nutrition Facts Labels, 2020 · 21 CFR 101.9, Nutrition labeling of food · Subhan FB et al. Ingestion of isomalto-oligosaccharides stimulates insulin and incretin hormone secretion, Journal of Functional Foods, 2020 · OFW Law, Low-Carb Food Labeling.