Understanding Net Carbs: How to Count Them Correctly
If you follow a low-carb or keto diet, "net carbs" is the number that matters. But calculating net carbs isn't always straightforward, especially with the introduction of allulose and the changing FDA labeling rules. Let's clear up the confusion once and for all.
What Are Net Carbs?
Net carbs represent the carbohydrates that your body actually absorbs and uses for energy — the ones that affect blood sugar and insulin.
The Basic Formula
Net Carbs = Total Carbohydrates – Fiber – Sugar Alcohols (– Allulose)
The subtracted components are carbohydrates that your body either:
- Cannot digest (fiber)
- Does not fully absorb or metabolize (sugar alcohols, allulose)
Breaking Down Each Component
Fiber
Fiber is a carbohydrate that humans cannot digest. It passes through the digestive system largely intact.
- Soluble fiber: Dissolves in water, forms a gel, may be partially fermented by gut bacteria. Subtract 100%.
- Insoluble fiber: Does not dissolve, adds bulk to stool. Subtract 100%.
Both types are subtracted entirely from net carbs because neither raises blood sugar.
Sugar Alcohols
Sugar alcohols (polyols) are partially absorbed. Different sugar alcohols have different absorption rates:
| Sugar Alcohol | % to Subtract | Net Impact |
|---------------|--------------|------------|
| Erythritol | 100% | Essentially zero impact |
| Xylitol | 50% | Moderate impact |
| Sorbitol | 50% | Moderate impact |
| Maltitol | 50% (some say only 25%) | Significant impact |
| Isomalt | 50% | Moderate impact |
| Mannitol | 50% | Moderate impact |
Important: Maltitol is the worst offender. Many "sugar-free" products use maltitol because it's cheap, but it has a glycemic index of 35 — meaning it meaningfully raises blood sugar. If a product lists maltitol, subtract only 25–50%, not 100%.
Erythritol is the only sugar alcohol you can subtract 100% with confidence.
Allulose
Allulose is in its own category:
- The FDA allows it to be excluded from Total Sugars and Added Sugars
- The FDA's guidance is less clear on whether it should be subtracted from Total Carbohydrates (different brands handle this differently)
- Metabolically, allulose should be subtracted 100% — it has zero glycemic impact
How to handle it on labels:
- Some labels already exclude allulose from Total Carbohydrates → no adjustment needed
- Some labels include allulose in Total Carbohydrates → subtract it
- Check the ingredients list and any voluntary allulose disclosure to determine which approach the manufacturer used
Practical Examples
Example 1: A Protein Bar
Label says:
- Total Carbohydrates: 22g
- Dietary Fiber: 9g
- Sugar Alcohols (erythritol): 8g
- Sugars: 1g
Calculation: 22 – 9 – 8 = 5g net carbs
Example 2: A Sugar-Free Cookie (with allulose)
Label says:
- Total Carbohydrates: 18g
- Dietary Fiber: 2g
- Total Sugars: 0g
- Ingredients include "allulose"
- Voluntary disclosure: Allulose 12g
Calculation: 18 – 2 – 12 = 4g net carbs
Example 3: A "Sugar-Free" Candy (with maltitol)
Label says:
- Total Carbohydrates: 25g
- Dietary Fiber: 0g
- Sugar Alcohols (maltitol): 20g
- Sugars: 0g
Conservative calculation: 25 – (20 × 0.5) = 15g net carbs
Aggressive calculation: 25 – 20 = 5g net carbs
The aggressive calculation is misleading because maltitol DOES raise blood sugar. The conservative calculation is more accurate for metabolic purposes.
Example 4: Whole Food (an avocado)
Nutrition:
- Total Carbohydrates: 12g
- Dietary Fiber: 10g
- Sugars: 1g
Calculation: 12 – 10 = 2g net carbs
Simple. Whole foods are straightforward because they don't contain sugar alcohols or allulose.
Common Mistakes
Mistake 1: Subtracting All Sugar Alcohols Equally
As shown above, erythritol (subtract 100%) and maltitol (subtract 25–50%) are very different. Read which specific sugar alcohol is used.
Mistake 2: Double-Counting Allulose Subtraction
If the manufacturer has ALREADY excluded allulose from Total Carbohydrates (as the FDA allows), don't subtract it again. You'd end up with artificially low net carbs.
Mistake 3: Ignoring Serving Size
A product might show 3g net carbs per serving, but if you eat three servings, that's 9g. Always check the serving size and adjust for what you actually consume.
Mistake 4: Trusting "Net Carbs" on Packaging
Many products display a "Net Carbs" count on the front of the package. This isn't an FDA-regulated number — the manufacturer calculated it using their own methodology. Always verify by doing the calculation yourself from the Nutrition Facts panel.
Mistake 5: Forgetting Hidden Carbs
Some ingredients contribute small amounts of carbs that add up:
- Heavy cream: 0.4g carbs per tablespoon (adds up in recipes)
- Eggs: 0.6g carbs per egg
- Cheese: 0.5–1g carbs per ounce
- Nuts: 1–4g net carbs per ounce
- Spices: Some contain carbs (garlic powder, onion powder)
Net Carb Targets
For Ketosis
Most people enter and maintain ketosis at 20–50g net carbs per day. The common starting point is 20g, with gradual increases to find your personal threshold.
For General Low-Carb
100–150g net carbs per day is considered low-carb (vs. the typical American intake of 250–300g).
For Diabetes Management
Work with your healthcare team. Typical recommendations range from 30–60g net carbs per meal.
The Allulose Advantage for Net Carb Counting
Allulose makes carb counting simpler and more enjoyable:
- Simple math: Allulose is always 0g net carbs, regardless of amount
- No gray areas: Unlike maltitol or sorbitol, you don't need to debate how much to subtract
- Consistent results: Blood sugar stays flat every time — no surprises
- More food freedom: Because allulose adds 0g net carbs, you can enjoy sweet foods without "spending" any of your daily carb budget
This means a slice of allulose cake might have 3g net carbs (from the almond flour and eggs), while a traditional cake slice has 40g+ net carbs. You get cake AND stay within your carb limits.
Quick Reference Card
| Ingredient | Subtract From Total Carbs? | Amount to Subtract |
|-----------|---------------------------|-------------------|
| Dietary fiber | Yes | 100% |
| Erythritol | Yes | 100% |
| Allulose | Yes (if included in Total Carbs) | 100% |
| Xylitol | Yes | ~50% |
| Sorbitol | Yes | ~50% |
| Maltitol | Yes | 25–50% |
| Stevia | N/A | N/A (used in tiny amounts) |
| Monk fruit | N/A | N/A (used in tiny amounts) |
Print this out, keep it in your wallet or on your phone, and you'll never be confused by a nutrition label again.