Lemon Curd

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

Also called jarred lemon curd, lemon cheese, lemon butter spread, lemon curd spread.

Lemon curd weighs about 320 g per US cup (11.3 oz) and 20 g per tablespoon, the figure Bonne Maman, Dickinson's and Tiptree print, a density of 1.353 g/mL. Butter-rich curds are probably a few percent lighter. King Arthur's 113 g per half cup would make a spread that is half sugar lighter than water and is rejected.

Lemon curd is lemon juice and zest cooked with sugar, eggs and butter until it thickens into a glossy spread. It is a British classic, sold in jars for toast and scones, and in baking it fills tarts, cakes, macarons and pavlovas. Jarred curds come in two kinds. Butter-and-egg curds such as Bonne Maman and Tiptree run about 13% fat with 54% sugars; budget curds, such as the UK supermarket own brands, use less butter and some water and starch, about 5% fat with 57% sugars.

USDA has no lemon curd record, and no source has weighed a whole cup, so confidence is low. The US labels are the evidence: Bonne Maman, Dickinson's and Tiptree all print 1 tablespoon at 20 g, which is 320 g per cup, and Bonne Maman's 18 servings in a 12.7-oz jar work out to the same 20 g. Stonewall Kitchen prints 15 g, and UK labels print 15 g for their 15 mL tablespoon; both make curd weigh about the same as water, which a product that is half sugar cannot, so those figures are not used here.

The physical check says the labels are close but probably a little high for the butteriest curds. Dissolved sugar makes a spread denser than water and butterfat makes it lighter. Working from Bonne Maman's composition, 13% fat, 55% carbohydrate and about 30% water, a curd should be about 1.26 g/mL, near 298 g per cup; a lower-fat budget curd about 1.29 g/mL, near 306 g. Jam, with no fat at all, is 1.35 g/mL and 20 g per tablespoon. So 20 g is right for jam and within about 5% for most curds, and a rich homemade curd may weigh closer to 300 g per cup. Whisking can also trap a little air.

King Arthur's chart lists lemon curd at 1/2 cup = 4 oz = 113 g. That is 227 g per cup, 0.959 g/mL, lighter than water. Half a cup is 4 fluid ounces, and 113 g is 4 weight ounces: the same fluid-ounce mistake behind King Arthur's 227 g cups of milk and cream. A spread that is about half sugar cannot weigh less than water, so the figure is recorded as a rejected source with its own correction page.

Practical guidance: 1 tablespoon is about 20 g and 1/4 cup about 80 g; for a rich homemade curd use 19 g and 75 g. A 10-oz jar holds 283 g, a little under 1 cup; an 11-oz jar 312 g, about 1 cup; a 12.7-oz jar 360 g, about 1 1/8 cups. For a tart, spoon the curd into the shell on the scale; curd clings to cups and spoons, and weighing avoids losing the last spoonful.

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

• King Arthur Baking Ingredient Weight Chart: 227 g per cup