A standard cup (240 mL) of oat milk contains roughly 14 to 18 grams of total carbohydrates, depending on the brand and whether it’s sweetened. That’s noticeably higher than most other plant milks and even cow’s milk. The carbs come almost entirely from oat starch that gets broken down into sugars during manufacturing, which is why oat milk tastes slightly sweet even without added sweeteners.
Carbs by Brand
The exact carb count shifts from brand to brand, but most fall within a narrow range. For a one-cup (240 mL) serving of original, unsweetened varieties:
- Oatly Original: 16 grams of carbs, 7 grams of sugar
- Silk Original: 18 grams of carbs, 7 grams of sugar
- Oatly Low Fat: 16 grams of carbs, 7 grams of sugar
Flavored or sweetened versions can push well past 20 grams per cup. If you’re tracking carbs closely, always check the label on the specific product you’re buying rather than relying on averages.
Why Oat Milk Has So Many Carbs
Oats are a grain, and grains are starchy. During production, manufacturers add a natural enzyme (alpha-amylase) that breaks oat starch into smaller sugars, primarily maltose. This step prevents the liquid from turning thick and gluey, and it gives oat milk its characteristic mild sweetness without needing to add table sugar. The result is that a large portion of the carbohydrates in your glass are simple sugars created during processing, not sugars that were added afterward.
This is worth understanding because a label might say “no added sugar” while still delivering 7 grams of sugar per cup. Those sugars are real and affect your blood sugar the same way. The fiber content, meanwhile, is low. Most commercial oat milks contain 0 to 2 grams of fiber per serving, meaning nearly all the carbs are digestible. Net carbs (total carbs minus fiber) typically land between 14 and 18 grams per cup.
How Oat Milk Compares to Other Milks
Oat milk sits at the higher end of the carbohydrate spectrum among common milks. For one cup of unsweetened versions:
- Oat milk: 14 to 18 grams of carbs
- Cow’s milk (whole): about 12 grams of carbs
- Almond milk: about 8 grams of carbs
- Soy milk: about 4 to 9 grams of carbs
Almond milk has roughly half the carbs of oat milk, which makes it a common swap for people on low-carb or ketogenic diets. Soy milk also comes in lower. Oat milk does offer more protein than almond milk (about 4 grams versus 1 gram per cup) and often more fiber, so the tradeoff depends on your priorities.
Is Oat Milk Okay on a Low-Carb Diet?
That depends on how strict your carb limit is. On a standard ketogenic diet aiming for under 20 to 50 grams of carbs per day, a single cup of oat milk eats up a significant chunk of your allowance. Two cups could take you to your limit before you’ve eaten any solid food. For someone following a moderate low-carb plan (under 100 to 150 grams per day), a splash in coffee or a cup with breakfast is easy to accommodate.
If you love the taste of oat milk but want fewer carbs, keep your portion small. A typical coffee shop “splash” is about 2 tablespoons, which contributes only 1 to 2 grams. A full latte with 8 ounces of oat milk, on the other hand, delivers the full 16 to 18 grams.
Homemade vs. Store-Bought
Homemade oat milk skips the enzymatic step that commercial producers use, so the starch stays largely intact rather than converting to maltose. This can mean a slightly different sugar profile and a thicker texture. Straining removes some of the starch and fiber, but the exact carb count varies widely based on your oat-to-water ratio and how thoroughly you strain.
The tradeoff is that store-bought oat milk is typically enriched with calcium, vitamin D, B vitamins, and iron. Homemade versions lack these additions. If you’re using oat milk as a dairy replacement and relying on it for those nutrients, commercial brands are the more reliable option.