If you’ve ever followed a recipe exactly and still ended up with a dry loaf or flat cookies, the measuring is usually to blame — not you. A “cup” is a measure of volume, but baking is chemistry that runs on weight, and the two don’t line up cleanly. This guide covers how to convert a recipe from cups to grams, why the same cup can weigh wildly different amounts, and when it’s worth reaching for a scale.
Why convert cups to grams at all
Grams are exact. A cup isn’t. Scoop flour one way and you get 125 g; scoop it another way and you get 155 g — a 20–30% swing from the same cup. Professional bakers and almost every recipe outside the US work in grams because weight removes that guesswork entirely. Converting to grams is how you make a recipe come out the same every single time.
The fast way: use the converter
For any single ingredient, the cups-to-grams converter gives you the exact weight instantly — pick the ingredient, type the amount, done. This guide is for understanding why those numbers are what they are.
How much does a cup actually weigh?
It depends entirely on the ingredient’s density. Here are the ones you’ll hit most often:
| Ingredient | 1 cup |
|---|---|
| All-purpose flour | 125 g |
| Granulated sugar | 200 g |
| Brown sugar (packed) | 220 g |
| Butter | 227 g |
| Powdered sugar | 120 g |
| Milk | 240 g |
Notice that a cup of flour (125 g) and a cup of sugar (200 g) are nowhere near each other. That’s the whole reason you can’t convert “cups to grams” with a single magic number — every ingredient is different.
Why the same cup weighs different amounts
Three things move the number: density (sugar is heavier than flour), packing (brown sugar pressed into the cup weighs far more than loose), and grind or cut (finely grated cheese packs denser than coarse shreds). This is also why your scoop technique matters so much for light, fluffy ingredients like flour.
How to measure each ingredient type correctly
Flour (spoon and level). Fluff it in the bag, spoon it loosely into the cup, then level the top with a straight edge. Never dip the cup into the bag — that compacts it and adds 20–30 g.
Brown sugar (packed). Press it firmly into the cup with the back of a spoon until it holds the cup’s shape like a sandcastle. Recipes assume packed.
Liquids vs dry. Use a clear liquid measuring cup at eye level for liquids, and flat-topped dry cups you can level for dry goods. They’re not interchangeable.
US vs UK vs metric cups
A US cup is 236.6 ml. A UK/Commonwealth cup is 250 ml, and a “metric cup” is also 250 ml — about 6% bigger. Use the wrong one across a whole recipe and the error compounds. Every number on this site uses the US cup; if your recipe is British or Australian, weighing in grams sidesteps the mismatch completely.
When cups are fine — and when to weigh
Cups are perfectly okay for forgiving, savory cooking and for ingredients that don’t compress, like granulated sugar or liquids. Weigh when precision matters: flour, in bread and pastry, and any time a bake has failed before. For tiny amounts — a few grams of salt or baking soda — a measuring spoon actually beats a cheap scale that can’t read below 2 g.
Keep the numbers handy
Bookmark the ingredient you use most, or grab the printable conversion chart — every ingredient plus oven temperatures on one page you can stick to the fridge.
All weights here are standard kitchen approximations based on the US cup (236.6 ml). Density varies with brand, grind and packing, so treat them as reliable guides rather than lab figures — which is exactly why, when it counts, you weigh.