Lemon zest

One US cup of lemon zest weighs 96 grams (3.4 ounces). Going the other way, 100 grams is about 1.04 cups.

Fresh herbs and aromatics compared: cup weights side by side, the source behind each, and why they differ.

A teaspoon of finely grated lemon zest weighs about 2 g and a tablespoon 6 g, loosely packed: USDA's record for lemon peel and Rose Levy Beranbaum's The Baking Bible give exactly the same figures. A cup, if a recipe ever asked for one, would be 96 g (3.4 oz).

Lemon zest is the thin, coloured outer layer of the peel, where the fruit's aromatic oil is held. It is grated off with a rasp-style grater such as a Microplane, leaving behind the white pith underneath, which is bitter. Bakers use it in cakes, cookies, scones, curds, glazes and shortbread, and cooks in pasta, risotto, gremolata, dressings and marinades. Recipes give it by the teaspoon or tablespoon, or as the zest of one or more lemons.

USDA's record for raw lemon peel weighs a tablespoon at 6 g and a teaspoon at 2 g. Rose Levy Beranbaum, whose recipes give both volume and weight, lists finely grated lemon zest at 1 tablespoon, loosely packed, 6 g, and at 2 tablespoons, loosely packed, 12 g, in The Baking Bible. The two sources agree exactly, so this site publishes 96 g a cup, 6 g a tablespoon, with high confidence.

The Culinary Institute of America's conversion chart says one medium lemon, zested, gives 2 teaspoons weighing 0.10 oz, 3 g. That is a yield from one fruit, rounded to the whole gram, and at 72 g a cup it is lighter than the two direct weighings; it is listed without a figure. How much zest a lemon gives varies with its size and with the grater: Rose Levy Beranbaum puts it at 1 1/4 to 2 teaspoons a lemon, the CIA at 2 teaspoons, and many recipes assume about a tablespoon.

The physical check: zest grated on a rasp comes off as fine, moist, oily threads of peel, each about as dense as water. Loosely packed, the threads tangle and hold a lot of air, filling about two-fifths of the spoon, which is 0.41 g/mL, 2 g a teaspoon. Pressed into the spoon the same zest weighs more, which is why Rose Levy Beranbaum specifies loosely packed.

Practical guidance: count 2 g a teaspoon and 6 g a tablespoon of finely grated lemon zest, spooned in lightly and leveled, not pressed. For a recipe that asks for the zest of 2 lemons, expect anything from 2 1/2 teaspoons to 2 tablespoons, 5 to 12 g, depending on the lemons; weigh it when lemon is the main flavour, as in a lemon cake, lemon bars or curd. Zest the lemon before juicing it, and grate just before using it, because the aromatic oil fades once the peel is cut. Dried lemon peel from the spice aisle is stronger and is not a spoon-for-spoon swap.