How much protein is in tofu?

The one plant protein that stands on its own

Most plant proteins come with an asterisk. Beans are low in methionine, grains are low in lysine, and the old advice was to pair them at the same meal so the amino acids add up. Tofu is the exception that makes the rule obvious. Because it’s made from soybeans, it carries all nine essential amino acids in genuinely usable amounts — its protein quality scores in the same league as eggs, dairy, and meat on the digestibility-corrected scales (PDCAAS and DIAAS) that nutritionists actually use. In plain terms: soy is a complete protein, and tofu doesn’t need a rice-and-beans partner to count. That’s the headline, and it’s why tofu shows up on this site as a real protein source rather than a “plant protein, with caveats” footnote.

The numbers back it up. This USDA reference — firm tofu set with calcium sulfate — runs 17.3 g of protein per 100 g, which works out to roughly 15 g in a 3 oz (85 g) serving and about 39 g in a full 8 oz block. For a food that’s also low in calories and carbs, that’s a strong return.

Firmness is the whole game

Here’s the gotcha that trips up shoppers: there is no single “protein in tofu” number, because firmness drives density. Tofu starts as soy milk that’s curdled and pressed, and how hard you press it decides how much protein ends up in each ounce. Silken tofu is barely pressed — it holds most of its water, so it’s soft, custardy, and comparatively dilute. Firm and extra-firm have had that water squeezed out, which concentrates the protein, the fat, and the minerals all at once. Same soybean, very different label.

This is also why pressing your own block at home isn’t a gimmick. Wrapping a firm block, weighting it, and draining off the water for twenty minutes doesn’t add a single gram of protein — but it removes the water that was diluting it, so the drained block weighs less and reads higher in protein per ounce. If you’re cooking to a protein target, start with firm or extra-firm and press it; if you’re making a smoothie or a silky dessert, silken is the right tool and you simply accept a lower number.

The calcium that hides in the coagulant

Tofu’s second trick is a mineral bonus most people don’t know to look for. To turn soy milk into curds, makers add a coagulant — and the most common one in the U.S., the one used in this exact USDA entry, is calcium sulfate. That single ingredient turns tofu into a legitimate calcium source: about 683 mg per 100 g, or more than 500 mg in a 3 oz serving — territory usually reserved for dairy. The catch is that it’s not automatic. Tofu set with nigari (magnesium chloride) is firmer-tasting but carries far less calcium. If you’re eating tofu partly for the bones, the move is to read the coagulant line on the package, not to assume.

Hitting a real protein goal with tofu

Put it together and tofu is one of the few plant foods you can build a meal around without apology. At roughly 15 g per 3 oz, two servings clear 30 grams — a square meal’s worth of complete protein, with the calcium riding along for free if you chose a calcium-set block. Where that fits into your total depends on your size and training; our protein-per-day guide walks through the math. And because the firm-vs-silken spread is so wide, the brand and cut you buy genuinely matter — the packaged tofus below are the firm and super-firm blocks worth reaching for when protein per ounce is the point.