How We Calculate Conversions

This page explains exactly how the conversions on Cups & Grams are calculated, so you can judge how much to trust them.

The cup we use

Every conversion uses the US customary cup of 236.588 ml, because that is the cup assumed by the great majority of online recipes. Note that a metric cup (250 ml) and a historic UK cup are different sizes — see our guide on US, UK and metric cups.

Why density matters

A cup is a unit of volume; a gram is a unit of weight. Converting between them requires the ingredient's density. We store a typical grams-per-cup figure for each ingredient and derive every other unit from it — tablespoons (a cup ÷ 16), teaspoons (a cup ÷ 48), millilitres, ounces (÷ 28.35 g) and pounds.

Where the figures come from

Grams-per-cup figures are compiled from the King Arthur Baking Ingredient Weight Chart, a long-established industry reference for baking measurements, and cross-referenced against the U.S. Department of Agriculture's FoodData Central database — the official scientific food-composition dataset maintained by the USDA Agricultural Research Service. Where sources differ slightly, we use a sensible typical value.

Rounding

Results are rounded for everyday kitchen use — generally to one or two decimal places. This is far more precise than a measuring cup, and appropriate for cooking and baking.

Disclaimer: ingredients vary. How tightly flour is packed, the humidity in your kitchen, and the brand all shift the real weight a little. Our figures are reliable typical values, not laboratory constants. For the most accurate results, weigh your ingredients with a digital scale.

Found an error?

If a figure looks wrong, please tell us via the contact page — ideally with a source.