Jam

One US cup of jam weighs 320 grams (11.3 ounces). Going the other way, 100 grams is about 0.31 cups.

Also called jam or preserves, fruit preserves, preserves, strawberry jam, strawberry preserves, grape jam.

Jam weighs 320 g per US cup (11.3 oz) and 20 g per tablespoon, a density of 1.353 g/mL. USDA and the Smucker's, Bonne Maman, Welch's and Kroger labels all give a tablespoon at 20 g. King Arthur's 85 g per quarter cup would make jam denser than honey and is rejected.

Jam and preserves are fruit cooked with sugar until enough water has gone that the mixture sets, usually with the fruit's own pectin or added pectin. US law treats them as one food: the standard of identity for fruit preserves and jams (21 CFR 150.160) lets the product be called either name and requires at least 65% soluble solids in the finished jar. Preserves keep larger pieces of fruit; jam is smoother. USDA's record for jams and preserves puts them at 30.5% water and 68.9% carbohydrate, 48.5% of it sugars, with almost no fat or protein.

USDA SR Legacy "Jams and preserves" (FDC 169641) lists 1 tablespoon at 20 g, which is 320 g per cup. Every mainstream label agrees: Smucker's jam and preserves, Bonne Maman preserves, Welch's Concord grape jam, Kroger and Blackburn's preserves all print 1 tablespoon at 20 g. US labels serve jam by the tablespoon, so these figures are the weight of a measured spoonful, rounded to the gram.

The physical check lands on the same number. A syrup of about 70% dissolved sugars and pectin is about a third denser than water. Working from USDA's composition, the sugars and other carbohydrate take up about 43 mL per 100 g and the water about 31 mL, so 100 g of jam fills about 74 mL: 1.35 g/mL, or 320 g per cup. Fruit pieces in preserves are mostly the same sugary syrup inside a cell wall, so preserves weigh the same per spoon as smooth jam.

Lower-sugar fruit spreads are a different product and a little lighter. Crofter's organic spread and Stonewall Kitchen's strawberry jam label a tablespoon at 18 g, 288 g per cup, which matches their lower sugar. Jelly, made from strained juice with no fruit pieces, has its own standard (21 CFR 150.140) and a similar sugar level.

King Arthur's chart lists "Jam or preserves" at 1/4 cup = 3 oz = 85 g, which is 340 g per cup and 1.437 g/mL. That is heavier than honey, which King Arthur itself lists at 21 g per tablespoon, 1.42 g/mL, and honey has about half as much water as jam. A quarter cup of jam really weighs 80 g, which is 2.8 oz; rounded up to 3 oz and converted back, it becomes 85 g. The figure is recorded as a rejected source with its own correction page.

Practical guidance: 1 tablespoon is 20 g, 1 teaspoon about 7 g, 1/4 cup 80 g and 1/2 cup 160 g. An 18-oz jar holds 510 g, about 1 1/2 cups; a 13-oz jar 369 g, a little over 1 cup. Jam is sticky, so for thumbprint cookies, Linzer bars or a cake filling, spoon it straight onto the scale rather than scraping out a measuring cup.

The following published figures for jam are rejected here, with the physics or standards reasoning behind each rejection on its own page:

• King Arthur Baking Ingredient Weight Chart: 340 g per cup