Basil Pesto

One US cup of basil pesto weighs 248 grams (8.7 ounces). Going the other way, 100 grams is about 0.40 cups.

Also called pesto, pesto sauce, jarred pesto, pesto alla Genovese, Genovese pesto, refrigerated pesto.

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

Basil pesto weighs 248 g per US cup (8.7 oz) and about 62 g per quarter cup, a density of 1.048 g/mL. USDA's three pesto records and the Classico, Buitoni, Rao's and Barilla labels all fall between 60 and 63 g per quarter cup. King Arthur's 28 g per 2 tablespoons would make pesto lighter than water and is rejected.

Pesto alla Genovese is basil pounded with olive oil, garlic, pine nuts, salt and hard cheese. Jarred and refrigerated pestos follow that recipe with variations: sunflower or canola oil in place of some olive oil, cashews in place of pine nuts, potato flakes or whey to bind. USDA's refrigerated pesto is 39% water and 38% fat; its shelf-stable pesto 43% water and 42% fat; Mezzetta's 50% fat. The oil is what keeps pesto close to the weight of water.

USDA SR Legacy lists refrigerated pesto (FDC 171579) at 63 g per quarter cup, 252 g per cup, with an identical Buitoni record; shelf-stable pesto (FDC 171580) at 61 g, 244 g per cup; and Mezzetta's basil pesto (FDC 171185) at 60 g, 240 g per cup. The labels sit between them: Classico and Buitoni at 62 g, Rao's at 63 g, Barilla, Kirkland and Great Value at 60 g. US labels serve pesto by the quarter cup, and the gram figure on them is the weight of that measured volume, so these are real weighings. This entry publishes 248 g, the Classico and Buitoni figure, in the middle of the spread.

The physical check works from USDA's compositions. Oil is lighter than water, about 0.92 g/mL; cheese protein, basil, nuts and salt are denser. For refrigerated pesto, those proportions predict about 1.05 g/mL, 249 g per cup; for Mezzetta's oilier pesto about 1.01 g/mL, 239 g. Both match the records to within a few grams. The oilier the pesto, the lighter the cup: a homemade pesto heavy on olive oil will sit at the low end.

King Arthur's chart lists basil pesto at 2 tablespoons = 1 oz = 28 g. That is 224 g per cup, 0.947 g/mL, lighter than even the oiliest pesto USDA lists. Two tablespoons are one fluid ounce, and 28 g is one weight ounce: the fluid ounce read as a weight ounce, the same mistake behind King Arthur's 227 g cups of water and milk. The figure is recorded as a rejected source with its own correction page. Kroger's Private Selection pesto, labeled at 57 g per quarter cup, is the one label close to it and sits outside the spread of every other source.

Practical guidance: 1/4 cup is 62 g, 2 tablespoons 31 g and 1 tablespoon 15.5 g. A 6.5- to 7-oz jar or tub holds 185-200 g, about 3/4 cup; an 8.1-oz jar 230 g, a little under 1 cup. For a pound of pasta, 1/2 cup (124 g) is a typical amount. Oil separates to the top of a jar, so stir before measuring; a scoop from the top is lighter, oilier pesto than a scoop from the bottom.

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

• King Arthur Baking Ingredient Weight Chart: 224 g per cup