Flaxseed is often praised for its omega-3 fatty acids and impressive fiber content, but its carbohydrate numbers need a second look when you track macros. A 100 g portion of raw flaxseed contains roughly 28.9 g of total carbohydrates, and 27.3 g of that is dietary fiber. That leaves only about 1.6 g of net carbs per 100 g — an unusually low value that makes flax a favorite on ketogenic and low-carb eating plans.
This calculator turns any flaxseed serving into usable carb data. Start by choosing whole seeds or ground flaxseed, enter your amount in grams, tablespoons, or cups, and the tool will show total carbs, fiber, net carbs, and the corresponding per-100 g values. It works for keto tracking, calorie counting, recipe scaling, or simply checking a label. Use the preset buttons for common serving sizes like a tablespoon of ground flax or a 28 g (1 oz) portion.
Estimate total carbs, fiber, and net carbs in any serving of flaxseed.
📊 Instant Results
How to Use This Calculator
Start by choosing the form of flaxseed you have — whole seeds or ground/milled flax — since the two forms have different volume-to-weight conversions. Next, enter your serving amount in grams, tablespoons, or cups. The calculator converts everything to grams first, then applies the per-100 g carbohydrate and fiber values for raw flaxseed. When you press Calculate Carbs, you get four key numbers: the actual serving weight, total carbohydrates, dietary fiber, and net carbohydrates.
The quick-fill buttons at the top let you test common portions instantly: a 7 g tablespoon of ground flax, a 10 g tablespoon of whole seeds, a 15 g serving, a 28 g (1 oz) portion, and a full 100 g reference amount. Use them to see how different serving sizes compare before entering your own amounts. The step-by-step breakdown below the results shows exactly how each figure was computed, so you can verify the math or explain it to a client, patient, or student.
How the Carb Values Are Derived
The calculator relies on the USDA FoodData Central food database for raw flaxseed, which lists 28.9 g of total carbohydrate and 27.3 g of dietary fiber per 100 g. Because dietary fiber is not digested into glucose the way starch and sugars are, many low-carb and ketogenic trackers subtract fiber from total carbohydrates to estimate net carbs. In this case, 28.9 g minus 27.3 g leaves roughly 1.6 g of net carbs per 100 g of flaxseed — an exceptionally low figure.
Whole and ground flaxseed share the same nutritional profile by weight, so the same per-100 g factors apply to both forms. What changes is the volume conversion: a tablespoon of whole seeds weighs about 10 g, while a tablespoon of ground flax weighs closer to 8 g, and a cup weighs 160 g versus 128 g. The calculator stores these density values and applies them automatically, so you can enter volume measurements with confidence.
Reference Conversions for Flaxseed
Volume measurements for flaxseed vary with packing, humidity, and the coarseness of the grind. The table below shows the standard reference weights used by this calculator, which are commonly cited for nutrition analysis.
| Flax form | 1 tablespoon | 1 cup | 28 g (1 oz) ≈ |
|---|---|---|---|
| Whole seeds | 10 g | 160 g | 2.8 tbsp |
| Ground / milled | 8 g | 128 g | 3.5 tbsp |
If your flaxseed is packed especially tightly or is extra finely ground, the actual weight per tablespoon can differ by a gram or two. When precision matters, weighing in grams is always the safer route.
Worked Examples
Example 1 — Ground flax in a smoothie: You add 2 tablespoons of ground flaxseed. Each tablespoon weighs 8 g, so the serving is 16 g. Total carbs = 16 × 0.289 = 4.6 g; fiber = 16 × 0.273 = 4.4 g; net carbs = 4.6 − 4.4 = 0.2 g.
Example 2 — Whole flax in baking: A recipe calls for ¼ cup of whole flax seeds. At 160 g per cup, that is 40 g. Total carbs = 40 × 0.289 = 11.6 g; fiber = 40 × 0.273 = 10.9 g; net carbs = 11.6 − 10.9 = 0.7 g.
Example 3 — Per 100 g reference: For a 100 g serving, total carbs = 28.9 g, fiber = 27.3 g, and net carbs = 1.6 g. This baseline is what makes flaxseed so popular for keto and low-carb meal plans.
Tips for Accurate Tracking
- Weigh in grams when possible. Spoon measurements of flaxseed vary with packing, moisture, and grind texture. A kitchen scale removes that uncertainty and makes your macro counts reproducible week after week.
- Check your brand's label. USDA reference values are averages for raw flaxseed. Some brands add sugar, honey, or other flavorings to their flax blends, which raises the carbohydrate count substantially. Always read the nutrition panel for the exact product you are eating.
- Remember that fiber still matters. Net-carbs-only tracking is useful for ketosis, but fiber has real effects on digestion, satiety, and gut microbiota. Treating fiber as zero does not mean it is physiologically invisible.
- Store ground flax properly. Milled flax is rich in omega-3 oils that can oxidize at room temperature. Keep it in an airtight container in the refrigerator or freezer to preserve both taste and nutrient content.
- Adjust for baked goods carefully. When flaxseed is used as an egg replacer or binder, the net carb figure stays essentially the same because flax does not lose significant carbohydrate to cooking.
Frequently Asked Questions
Is flaxseed a low-carb food?
Yes, by net carbs. With roughly 1.6 g of net carbs per 100 g, flaxseed is among the lowest-carb seeds you can buy. The practical caveat is portion control: a 100 g serving also delivers about 534 calories, so a large flax-heavy snack can still overwhelm an energy budget even if the carb count stays low.
Why does a tablespoon of whole flax weigh more than ground flax?
Whole seeds are smooth and round, so they leave air gaps in a measuring spoon. Ground flax packs more densely into the same volume. Reference data puts a tablespoon of whole flax at about 10 g and ground flax at about 8 g, which is why the volume-to-gram conversion depends on the form you select.
Can I use this calculator for flax flour or flax meal?
Flax meal and milled flaxseed are essentially the same product, so the ground-flax setting applies. Flavored or sweetened blends may contain added sugar, molasses, or starch fillers, so check the ingredient list before using these base values. Golden flax has a macro profile similar to brown flax, so no separate setting is needed.
Is cooked or raw flaxseed nutritionally different?
For carbohydrate and fiber, the difference is negligible. Cooking affects moisture and some heat-sensitive nutrients, but fiber and carb content stay effectively constant, so the same per-100 g factors work for flax used in baking, porridge, or other cooked dishes.