How many carbs are in tofu?

Tofu is one of the rare complete proteins you can treat as effectively carb-free. A 3 oz serving of firm tofu (85 g) carries just about 2.4 g of total carbohydrate — that’s 2.8 g per 100 g — and a full 8 oz block holds only around 6.4 g. Subtract the fiber and the number that matters for low-carb eating drops to roughly 0.4 g net carbs per serving. There’s no meaningful sugar in the mix either. For a food delivering ~15 g of high-quality protein per serving, that’s an unusually clean carb profile, and it’s why tofu shows up as the protein in so many keto and low-carb meals.

Why the net carbs are almost nothing

Net carbs are total carbs minus fiber, and tofu’s total is so small to begin with that what’s left is negligible. About 2.0 g of the 2.4 g in a serving is fiber — the indigestible part that passes through without raising blood sugar — leaving roughly 0.4 g of digestible carbohydrate. And unlike beans or lentils, tofu carries no real sugar and only trace starch, because the carb-heavy parts of the soybean don’t survive the journey into a pressed curd. The result is a protein that behaves nothing like the other plant proteins it’s often grouped with: black beans and lentils bring 20+ g of carbs per serving, while firm tofu barely registers.

The keto and low-carb verdict

Firm tofu is about as keto-friendly as a complete protein gets. At ~0.4 g net carbs per 3 oz, you could eat an entire 8 oz block — roughly 1.4 g net — and barely register against a strict 20 g keto budget, while banking about 39 g of complete protein and a dose of calcium if it’s the calcium-set kind. That combination is hard to find in the plant world: most low-carb plant foods are fats (avocado, nuts) rather than proteins. Tofu lets you hit a real protein target on keto without an animal product and without spending your carb allowance. One practical note — firmness shifts the numbers slightly (silken reads a touch lower per gram, firm a touch higher once pressed), but every cut of plain tofu lands in the same near-zero-net-carb territory.

Tofu’s low carbs are only half its appeal — the protein quality is the other half. For why soy counts as a complete protein when beans and grains don’t, see protein in tofu. And for any packaged or flavored tofu, read the label’s own carb and sugar lines, since marinades and sauces can add both.