Fish sauce

One US cup of fish sauce weighs 283.9 grams (10 ounces). Going the other way, 100 grams is about 0.35 cups.

Also called nam pla, nuoc mam, Thai fish sauce, Vietnamese fish sauce, patis, anchovy fish sauce.

Condiments and sauces compared: cup weights side by side, the source behind each, and why they differ.

A cup of fish sauce weighs 283.9 g (10 oz), a density of 1.20 g/mL, so a tablespoon weighs 17.7 g and a teaspoon 5.9 g. A 700 mL bottle of Tiparos fish sauce has a net weight of 840 g, and USDA and Red Boat both weigh a tablespoon at 18 g. Fish sauce is one of the heaviest thin liquids in the kitchen, about a fifth heavier than water.

Fish sauce is made by layering anchovies or other small fish with salt and leaving them to ferment for months to a year or more; the liquid that drains off is the sauce. Thai nam pla, Vietnamese nuoc mam and Filipino patis are all made this way. It is clear, thin and amber to dark brown, and it is used by the teaspoon in dressings, dipping sauces, curries, stir-fries and marinades.

Its weight comes from salt. USDA's Standard Reference record for ready-to-serve fish sauce (FDC 174531) lists 7,851 mg of sodium per 100 g, which is about 20% salt, plus 5 g of protein and 3.6 g of sugars dissolved from the fish, with 71% water. A plain brine of 20% salt weighs 1.15 g/mL, and the dissolved protein adds the rest. That predicts about 1.19 to 1.20 g/mL before anything is weighed.

Three sources agree within 1.4%. The technical sheet for a 700 mL bottle of Tiparos, a Thai brand, gives a net weight of 0.84 kg: 1.200 g/mL, 283.9 g per cup. USDA's record weighs 1 tablespoon at 18 g, 288 g per cup, and Red Boat's label gives the same 1 tablespoon (18 g). Whole-gram rounding on a tablespoon allows anything from 17.5 to 18.5 g, so the tablespoon figures support the bottle rather than compete with it. The bottle, 840 g over 700 mL, is the most precise of the three and is published.

Fish sauce shows how far a salty liquid sits from water. A tablespoon weighs 17.7 g, 20% more than the 14.8 g of a tablespoon of water, and a cup weighs 47 g more than a cup of water. Soy sauce, with about 14% salt plus dissolved soybean solids, weighs a little less, 277.6 g per cup.

Practical guidance: use 283.9 g per cup, 71 g per quarter cup, 17.7 g per tablespoon and 5.9 g per teaspoon. Strength varies between brands, but every bottled fish sauce is a strong brine, so the figure holds closely across them. Vietnamese nuoc cham, the dipping sauce made by diluting fish sauce with water, lime juice and sugar, is a different product and much lighter. A teaspoon of fish sauce carries about 460 mg of sodium, so weigh it when cooking for a low-sodium diet.