2026-09-13 · Keto Food Verdicts · 2971 words · Lab-Verified Data

Is Soy Sauce Keto? Net Carbs in Soy Sauce, Tamari and Low-Sodium

The Verdict First

Soy sauce clears both lines, and the carbohydrate figure is not the interesting part. At 4.13 g net carbs per 100 g (USDA SR Legacy, FDC #174277), it sits 0.87 g under our keto threshold, so it earns a plain yes on both the keto and low-carb badges. Very few condiments that taste like anything get to say that.

The number that actually decides how you use the bottle is sodium. The same 100 g holds 5,493 mg of sodium (FDC #174277). A level tablespoon of soy sauce weighs about 16 g, which puts roughly 879 mg of sodium — and about 0.66 g of net carbs — into whatever you are cooking. That is 38 percent of the FDA Daily Value for sodium, against 3 percent of a typical daily carbohydrate budget. The carbohydrate is a rounding error. The salt is the decision.

There is a second split worth knowing before you shop, and it comes straight out of the USDA records rather than from marketing. USDA keeps five separate entries for the brown liquid in the bottle, and the net carb figure moves from 4.13 g to 14.14 g across them. The gap tracks how the sauce was made, not how dark it looks. Two of those forms land above our keto line, and one of them is the "reduced sodium" version, which is worth reading twice.

So the short answer is yes, soy sauce is keto-friendly at any normal pour, and the measured reason is that you use so little of it that the carbohydrate never becomes the constraint. The longer answer is about which bottle, and that is what the rest of this page works through.

The Numbers, per 100 g

The card above is pulled directly from USDA FoodData Central and is never hand-copied. Four details in it matter more than the rest.

Sugar is almost absent. Standard soy sauce carries 0.4 g of sugar inside a 4.93 g total carbohydrate figure (FDC #174277) — under 10 percent of the total. That is unusual for a condiment, and it is the main reason the net carb number stays low. Ketchup, teriyaki and hoisin all get their carbohydrate load from added sweetener; fermented soy sauce gets most of its from the wheat and soybean solids that survive fermentation. Subtract the 0.8 g of fiber and you land at 4.13 g net. Our net carbs guide covers why that subtraction, rather than total carbohydrate, is the figure we publish.

The protein is not trivial. At 8.14 g per 100 g with 0.57 g of fat and 53 kcal (FDC #174277), soy sauce has more protein per 100 g than most sauces. You will never eat 100 g of it, so this does not make it a protein source — but it does tell you what the liquid is: fermented bean solids in brine, not a sweetened syrup.

Potassium is high and so is sodium. The record shows 435 mg of potassium, 74 mg of magnesium and 5,493 mg of sodium per 100 g (FDC #174277). For scale, 100 g of raw cauliflower carries 299 mg of potassium and 30 mg of sodium (FDC #169986). Soy sauce is roughly 183 times saltier than cauliflower by weight. Our keto flu and electrolytes guide works through why sodium is the mineral low-carb eaters track most closely, and what that means for a condiment like this one.

There is no cholesterol and almost no saturated fat — 0 mg and 0.07 g respectively (FDC #174277). If you are tracking a fat ratio, soy sauce contributes essentially nothing to either side of it.

Five Forms, Five Numbers: Why the Bottle Matters

USDA does not publish one entry for soy sauce. It publishes five, and they are not variations of the same measurement. Each is a distinct record with its own FoodData Central ID, and the spread between them is wider than the spread between whole milk and skim milk.

Net carbs and sodium per 100 g, by soy sauce type

USDA record	Net carbs / 100 g	Sodium / 100 g	FDC ID
Soy and wheat (shoyu)	4.13 g	5,493 mg	174277
Soy only (tamari)	4.77 g	5,586 mg	174278
Shoyu, low sodium	4.89 g	3,598 mg	172473
Hydrolyzed vegetable protein	7.34 g	6,820 mg	174279
Reduced sodium, hydrolyzed	14.14 g	2,890 mg	172474

Source: USDA FoodData Central, SR Legacy. Net carbs = total carbohydrates − fiber. Each row is a separate USDA record. All five are shelf-stable liquids sold as soy sauce in the United States.

Read the first three rows as one group. Traditional fermented soy sauce — whether it is made from soy and wheat or from soy alone — stays under 5 g net carbs per 100 g. Tamari edges slightly higher at 4.77 g (FDC #174278) because it skips the wheat but concentrates more bean solids, and the low-sodium shoyu comes in at 4.89 g (FDC #172473). All three are keto-friendly at real-world amounts.

The last two rows are a different manufacturing story. Hydrolyzed vegetable protein soy sauce is made by breaking down defatted soy with acid rather than fermenting it with a mold culture, a process measured in hours instead of months. Its record reads 7.34 g net carbs per 100 g (FDC #174279) — 78 percent higher than traditional shoyu, and past our keto line. Fast soy sauce is not the same food as fermented soy sauce, and the carbohydrate line is where the difference shows up.

Then the row that surprises people: the reduced-sodium hydrolyzed version measures 14.14 g net carbs per 100 g (FDC #172474), nearly double the full-sodium version of the same process. Cutting the salt does not cut the carbohydrate. In this record the sugar figure rises to 5.63 g against 1.3 g, which tells you where the missing sodium went — something else went into the bottle. "Low sodium" and "low carb" are two independent claims, and this entry is the cleanest proof of that we can put on the page.

What a Real Portion Costs

Nobody eats 100 g of soy sauce. The useful numbers are the small ones, and here they are, run on the USDA figures above.

• 1 tsp (about 5 g) — 0.21 g net carbs, 275 mg sodium
• 1 tbsp (about 16 g) — 0.66 g net carbs, 879 mg sodium
• 1 oz (28.35 g) — 1.17 g net carbs, 1,557 mg sodium
• 2 tbsp (about 32 g) — 1.32 g net carbs, 1,758 mg sodium

Now run the arithmetic to its end, because it settles the question cleanly. To reach our 5 g keto line using soy sauce alone, you would have to use about 121 g of it — roughly seven and a half tablespoons. That pour would deliver 6,646 mg of sodium, which is 289 percent of the FDA Daily Value of 2,300 mg and more than a full day's worth several times over.

That is the whole answer to whether soy sauce fits a low-carb pattern, and it has nothing to do with carbohydrate. You cannot physically eat enough soy sauce for the carbs to matter; you can easily use enough for the salt to matter. One tablespoon in a stir-fry is 0.66 g net carbs and 38 percent of your sodium budget. Two tablespoons is 1.32 g and 76 percent. The carbohydrate column stays boring while the sodium column fills up.

For anyone tracking electrolytes rather than just macros, that sodium is not automatically a problem — it is the same mineral that low-carb eaters often come up short on. The point is that the bottle is a dosing device, and the dose you are choosing is measured in milligrams of sodium, not grams of carbohydrate.

How to Use It — and What to Swap In

On low-carb, soy sauce is a free condiment at normal amounts. On keto, it is also free at normal amounts, for the measured reason above. Those two lines sit in different places, and our keto vs low-carb comparison works through where they diverge and why a food can earn a yes on one badge and a caution on the other. The only version worth avoiding on a keto pattern is the hydrolyzed vegetable protein bottle at 7.34 g per 100 g (FDC #174279) — not because a tablespoon of it will hurt you, but because you would rather spend your carbohydrate budget on food than on sauce.

When you do want to cut the sodium without losing the savory note, these are the verified alternatives in our library, all measured per 100 g:

Condiments compared: net carbs and sodium per 100 g

Condiment	Net carbs / 100 g	Sodium / 100 g	FDC ID
Vinegar, distilled	0.04 g	2 mg	172237
Pepper sauce (Tabasco)	0.2 g	633 mg	174528
Vinegar, cider	0.93 g	5 mg	173469
Fish sauce	3.64 g	7,851 mg	174531
Soy sauce (shoyu)	4.13 g	5,493 mg	174277
Soy sauce, low sodium	4.89 g	3,598 mg	172473
Oyster sauce	10.62 g	2,733 mg	174529
Teriyaki sauce	15.46 g	3,833 mg	171167
Sriracha	16.96 g	2,124 mg	171186
Worcestershire sauce	19.17 g	1,300 mg	171610
Hoisin sauce	41.28 g	1,615 mg	172886

Source: USDA FoodData Central, SR Legacy. Net carbs = total carbohydrates − fiber. All values are per 100 g of the product as sold.

Low-sodium soy sauce is the closest one-for-one swap. It cuts sodium by 34 percent (5,493 mg down to 3,598 mg at FDC #172473) and adds only 0.76 g of net carbs per 100 g. At a tablespoon, that is 576 mg of sodium instead of 879 mg. If you use soy sauce several times a day, this is the single change that moves your numbers most.

Fish sauce is not a lower-sodium substitute, despite being thinner. At 7,851 mg of sodium per 100 g (FDC #174531) it is saltier than soy sauce by 43 percent, though it carries less carbohydrate at 3.64 g. A little goes a long way, and a little is what you use.

Vinegar and pepper sauce are the near-zero options. Distilled vinegar measures 0.04 g net carbs and 2 mg sodium per 100 g (FDC #172237), and Tabasco-style pepper sauce measures 0.2 g and 633 mg (FDC #174528). Neither delivers the fermented umami of soy sauce, but both let you add acidity and heat without touching either column.

One gap worth naming honestly: coconut aminos does not have a verified entry in the SR Legacy dataset we build from, so we publish no number for it rather than guess one. If you are comparing bottles in a store, the USDA records above are the ones we can stand behind.

A Keto Recipe: Sesame-Soy Smashed Cucumber

Smashed cucumber is the fastest way to use soy sauce well, because the technique makes the dressing go further than the amount suggests. Smashing the cucumber breaks the cell walls so the seasoning gets in without needing a long marinade — which means you use two teaspoons of soy sauce instead of two tablespoons and get the same effect. It is the same bottle that does the seasoning work in our cauliflower rice stir-fry, where one tablespoon covers two servings.

Keto build (one serving, under 5 g net carbs): 200 g cucumber, peeled · 2 tsp soy sauce · 2 tsp sesame oil · 1 small clove garlic, minced · 3 g fresh ginger, grated

Low-carb build (one serving, under 20 g): 400 g cucumber, peeled · 1 tbsp soy sauce · 1 tbsp sesame oil · 2 cloves garlic, minced · 6 g fresh ginger, grated · 100 g green bell pepper, sliced thin

1. Lay the cucumber on a board and press down on it with the flat side of a chef's knife until it splits along its length, then break it into rough 3 cm pieces. You want cracks, not clean slices — the cracks are what hold the dressing.
2. Toss the pieces with a pinch of salt and leave them in a colander for ten minutes. Cucumber is mostly water, and the salt pulls some of it out; pour that liquid off rather than letting it dilute the dressing. Most of the salt you added leaves with it.
3. Whisk the soy sauce, sesame oil, garlic and ginger in the bottom of the bowl. Grate the ginger rather than chopping it — the fibers are tough, and grating distributes the flavor through the oil.
4. Add the drained cucumber and toss. Let it sit ten minutes before serving. It will not keep much past an hour once dressed, because the cucumber keeps releasing water.

By the numbers: the keto build runs about 4.45 g net carbs — 2.92 g from the cucumber (FDC #169225, at 1.46 g per 100 g), 0.44 g from the soy sauce (FDC #174277, at 4.13 g per 100 g), 0.62 g from the garlic (FDC #169230, at 30.96 g per 100 g) and 0.47 g from the ginger (FDC #169231, at 15.77 g per 100 g). The sesame oil contributes 0 g (FDC #171016). The low-carb build runs about 11.94 g net carbs, with the bell pepper adding 2.94 g (FDC #170427, at 2.94 g per 100 g) and the larger garlic and cucumber amounts making up the rest.

Sodium tracks the soy sauce: about 590 mg in the keto build and about 890 mg in the low-carb build. The cucumber, garlic and ginger add a few milligrams each, and the sesame oil adds none.

Fun Fact: The Same Brown Liquid, Five USDA Records

The reason USDA keeps five entries instead of one is that the bottle labeled "soy sauce" can be made two entirely different ways, and the agency measures each separately.

Traditional soy sauce is a fermentation product. Soybeans — and usually wheat — are inoculated with Aspergillus mold cultures, then left in brine for months while enzymes break the proteins and starches down. That process takes time, and it produces the layered savory flavor that made the condiment worth carrying across the world. The USDA names for those entries tell you the recipe: "made from soy and wheat (shoyu)" and "made from soy (tamari)." Wheat is the difference between the two names, and it is also why traditional tamari is the one that people avoiding gluten reach for — historically it was drawn off as a byproduct of miso fermentation, which does not call for wheat at all.

The other path skips the mold entirely. Hydrolyzed vegetable protein sauce is made by treating defatted soy with acid under heat, which breaks the protein down in hours rather than months. The result is cheaper and saltier — 6,820 mg of sodium per 100 g in the USDA record (FDC #174279) — and, per the same record, higher in carbohydrate at 7.34 g net per 100 g.

So the five entries are not a data quirk. They are a compressed history of how one condiment got industrialized, and the net carb column is where the shortcut shows.

Is soy sauce keto-friendly?

Yes, at any normal amount. Standard fermented soy sauce measures 4.13 g net carbs per 100 g (USDA SR Legacy, FDC #174277), which is under our 5 g keto threshold. Since a level tablespoon weighs about 16 g, one tablespoon adds roughly 0.66 g net carbs. The constraint to watch is sodium rather than carbohydrate: the same tablespoon carries about 879 mg of sodium, 38 percent of the FDA Daily Value. The one form worth avoiding on keto is hydrolyzed vegetable protein soy sauce at 7.34 g net carbs per 100 g (FDC #174279), which sits above the line.

How many carbs are in a tablespoon of soy sauce?

About 0.66 g net carbs, using 4.13 g per 100 g (FDC #174277) and a 16 g tablespoon. A teaspoon works out to roughly 0.21 g. Both numbers are small enough that soy sauce will not move a daily carbohydrate total in any meaningful way. The same tablespoon contributes about 879 mg of sodium, which is the figure worth writing down if you use the bottle daily.

Is tamari better than regular soy sauce for keto?

Not on carbohydrate. Tamari measures 4.77 g net carbs per 100 g against 4.13 g for shoyu (FDC #174278 vs #174277), so it is marginally higher, and both are comfortably under the keto line. Tamari's actual advantage is in the ingredient list rather than the carbohydrate column: the USDA record is named "made from soy (tamari)" while the shoyu record is "made from soy and wheat," which reflects the traditional wheat-free fermentation path. If you are avoiding wheat, that distinction is the reason to choose it.

Is low-sodium soy sauce lower in carbohydrates?

Not necessarily — and in one case, the opposite. Low-sodium shoyu measures 4.89 g net carbs per 100 g against 4.13 g for the standard version (FDC #172473 vs #174277), so it is slightly higher while cutting sodium by 34 percent. The reduced-sodium hydrolyzed vegetable protein version is the extreme case, at 14.14 g net carbs per 100 g (FDC #172474) — nearly double the full-sodium hydrolyzed record, with sugar rising to 5.63 g. Treat "low sodium" and "low carb" as separate claims and check both numbers on the label.

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