Gram (g)

The gram is the small metric unit of mass that kitchen scales, food labels and recipes outside the US rely on. Yeast, salt and spices are measured a few grams at a time, while flour and sugar run to hundreds.

When France built the metric system in the 1790s, the gram was its unit of mass, tied to the weight of one cubic centimeter of water (NIST Handbook 44, Appendix B). The kilogram later became the base unit, and today the gram is defined from it.

That history explains a naming rule: SI prefixes attach to the gram, not the kilogram. A millionth of a kilogram is written as a milligram (mg), never a "microkilogram" (NIST SP 330).

A cup of flour changes with how you fill it, but 100 g of flour is always the same amount. That is why many baking recipes, especially British and European ones, list flour, sugar and butter by weight.

Grams also make recipes easy to scale: to halve a bread recipe, halve each number. A digital scale with a tare button lets you weigh everything into one bowl, and the cups to grams converter helps when a recipe only gives cups.

On a US Nutrition Facts label, a serving size in cups, pieces or slices is followed by its weight in grams, or by milliliters for drinks (21 CFR 101.9). Fat, carbohydrate and protein are listed in grams too, while sodium is listed in milligrams.

That makes grams the easiest way to compare two products. Check the grams per serving first, then the number of servings in the package.