Tofu Nutrition Facts: Calories, Complete Protein, and Isoflavones

A 100-gram serving of firm tofu provides 144 calories, 17.3g of protein (all 9 essential amino acids), 683mg of calcium (53% of daily value), and 25-50mg of isoflavones. Despite its reputation as a bland, textured block, tofu is one of the most nutrient-dense and versatile plant-based whole foods available — and the science supports its cardiovascular and bone health benefits.

This guide pulls nutrition data from USDA FoodData Central (firm tofu, prepared; NDB 16110) and explains what tofu’s numbers mean across cooking methods, firmness types, and the myths that persist around soy.

Tofu Nutrition Facts (per 100g, firm tofu, calcium-set)

Nutrient	Amount	% Daily Value*
Calories	144 kcal	7%
Total Fat	8.7 g	11%
— Saturated Fat	1.3 g	7%
— Monounsaturated Fat	1.9 g	—
— Polyunsaturated Fat	4.9 g	—
Carbohydrates	2.8 g	1%
— Dietary Fiber	2.3 g	8%
— Sugars	0.1 g	—
Protein	17.3 g	35%
Calcium	683 mg	53%
Iron	2.7 mg	15%
Magnesium	111 mg	26%
Manganese	1.9 mg	83%
Phosphorus	293 mg	23%
Isoflavones (total)	25–50 mg	—

*Daily Values based on a 2,000-calorie reference diet (FDA). Individual needs vary.

For a typical serving (200g block of firm tofu), multiply each value by 2. For silken or soft tofu, protein and calcium remain per gram of solids; the visible difference is higher water content.

Tofu Is a Complete Plant Protein

Soy is one of only a handful of plant sources that contain all nine essential amino acids in measurable amounts. A 100g serving of firm tofu delivers:

• Leucine — ~2.0g (critical for muscle protein synthesis)
• Isoleucine — ~0.95g
• Valine — ~0.95g
• Methionine — ~0.3g
• Cysteine — ~0.15g
• Phenylalanine — ~1.0g
• Tyrosine — ~0.7g
• Tryptophan — ~0.3g
• Threonine — ~0.75g
• Lysine — ~1.3g

The PDCAAS (Protein Digestibility-Corrected Amino Acid Score) for soy protein is 0.91–1.0, meaning it rivals or matches the bioavailability of animal proteins like beef or eggs. A 200g serving of firm tofu (35g protein) covers most of an adult’s daily protein need; pair it with whole grains (rice, quinoa, bread) and you easily reach amino acid completeness in a single meal.

This is why tofu has been a staple in Asian diets for over 2,000 years and why modern plant-based athletes rely on it.

The Calcium Story: Set with Calcium Sulfate or Nigari

Tofu’s calcium content depends entirely on the coagulant used during production. This is crucial:

Calcium-set tofu (coagulated with calcium sulfate or gypsum) contains 600–700 mg per 100g — a meaningful amount for bone health, muscle function, and heart rhythm. Many Western tofu brands use calcium sulfate specifically because the coagulant adds nutrition and firm texture. A 200g block provides 1,200+ mg of calcium — nearly the entire daily recommendation for adults.

Nigari-set tofu (coagulated with magnesium chloride) contains very little bioavailable calcium — perhaps 100–200 mg per 100g. It has a silkier texture, which is why Japanese regional preferences lean this direction, but it offers no dietary calcium advantage.

Always check the ingredient list or nutrition panel. If the label says “calcium sulfate” or “gypsum,” you’re getting 50% of your daily calcium in a single serving. If it lists “nigari” or “bittern,” calcium from tofu is not a significant dietary source for you — supplement elsewhere or choose a calcium-set variety.

Isoflavones, Estrogen, and the Myths That Won’t Die

Tofu contains phytoestrogens — specifically, the isoflavones genistein and daidzein, totaling 25–50 mg per 100g. For decades, scare headlines claimed that soy “feminizes men” or “feeds breast cancer.” Modern evidence has thoroughly debunked this.

The science:

• A 2021 meta-analysis in Nutrients examined 18 randomized controlled trials (over 2,000 participants). Result: soy isoflavone consumption did not raise circulating estrogen levels or lower testosterone in men. Breast tissue density in women was unchanged.
• The American Cancer Society affirms that soy foods are safe and may even reduce the risk of breast cancer recurrence in survivors (American Cancer Society).
• Harvard Nutrition Source states: “There is no convincing evidence that soy foods or isoflavones increase the risk of breast cancer” (Harvard T.H. Chan School of Public Health).

Why the confusion? Isoflavones are structurally similar to estrogen and can bind estrogen receptors in lab dishes, but in the human body at normal dietary intake (25–50 mg/day), they act as weak partial agonists — far too weak to meaningfully alter hormone levels. Asian populations consume soy throughout life with no observed feminization or cancer surge; if the estrogen story were true, you’d see it in epidemiology.

Bottom line: Eating tofu does not increase your cancer risk or alter your hormone profile. It is a safe, nutrient-dense food.

Firmness Matters: Silken, Soft, Firm, and Extra-Firm

All tofu starts as soy milk coagulated into curds and pressed into blocks. The firmness depends on how much water is pressed out — not on different varieties or processing:

Firmness	Water Content	Use Cases	Protein per 100g
Silken	90%+	Blended soups (miso soup), smoothies, desserts (silken pudding), sauces	~8g
Soft	~80%	Scrambling, light stir-fries, hot-pot broths, gentle cubed dishes	~12g
Firm	~70%	Pan-frying, marinating, stir-fries, pressing for texture	~17–18g
Extra-firm	~60%	Deep-frying, grilling, dicing into salads, high-heat cooking	~18–19g

Nutrition is per actual protein/solids, not per 100g of the block. A 100g block of silken tofu has less total protein than a 100g block of firm tofu because it’s mostly water. If you want maximum protein, buy extra-firm.

For flavor and texture, pressing firm or extra-firm tofu before cooking is essential: wrap it in a clean towel, place it on a plate, weight it with a heavy pan, and let it sit 15–30 minutes. This removes water and allows marinades to penetrate, salt to season the interior, and heat to create a crust.

Cooking Tofu: Pressing, Marinating, and High Heat

Tofu tastes like the food it’s cooked with — it has a mild, slightly beany base note that disappears when paired with bold seasonings.

Standard method:

1. Press the block (15–30 min) to remove excess moisture.
2. Cube, slice, or crumble the tofu.
3. Marinate in soy sauce, sesame oil, garlic, ginger, or vinegar for 30 minutes.
4. Pan-fry in neutral oil over medium-high heat until edges are golden (3–4 min per side for cubes).
5. Finish with a glaze (soy + rice vinegar + honey + sesame oil) or fold into a stir-fry.

Common mistakes:

• Not pressing — tofu will be soggy and won’t brown.
• Cooking over low heat — the surface won’t crisp and won’t develop flavor.
• Adding salt before pressing — it draws out more water.
• Scrambling without pressing — it falls apart.

Scrambled tofu: Press firm tofu, crumble it by hand, then stir-fry in a large skillet with oil, salt, turmeric, nutritional yeast, and vegetables. It mimics scrambled eggs in texture and can be a high-protein breakfast.

When Tofu Might Not Fit Your Diet

• Soy allergy — True soy allergies are rare (about 0.4% of the population) but serious; tofu is off the table if you have one. Soy allergy cross-reacts with peanut allergy in some individuals.
• Thyroid concerns at extreme intake — Soy contains compounds (goitrogens) that can interfere with iodine absorption only at very high doses (multiple servings daily for months without adequate iodine intake). For anyone with hypothyroidism: eating tofu in normal amounts (1–2 servings per day) is safe. Ensure adequate iodine (table salt, seaweed, fish, eggs) and take thyroid medication 4+ hours away from soy. Consult your endocrinologist.
• Low-FODMAP diet — Tofu is low in FODMAPs and generally tolerated by IBS patients. Firm tofu is lower-FODMAP than silken (silken still tolerable in small amounts).
• GMO concerns — Most soybeans in North America are genetically modified. If you prefer non-GMO tofu, look for certified organic or non-GMO labels; expect higher price.
• Preference for whole plant foods — Tofu is processed (soy milk → coagulated curds → pressed). Some dietary patterns (whole food plant-based, traditional diets) emphasize whole soybeans, edamame, tempeh, or miso instead.

The Bottom Line

A 200-gram serving of firm, calcium-set tofu: ~288 calories, 35g of complete plant protein, 1,366mg of calcium (68% of daily value), and 50–100mg of isoflavones. It is one of the most nutrient-dense plant proteins available and has been safely consumed by billions across Asia for millennia. The “soy estrogen” panic has no scientific foundation. Press it, marinate it, and cook it hot — and it rivals the flavor and satisfaction of animal-based meals.