The Problem with Measuring by Volume
A cup is a fixed volume — 236.6 milliliters. But baking ingredients don't all weigh the same per volume. One cup of all-purpose flour weighs about 125 grams. One cup of granulated sugar weighs about 200 grams. One cup of butter weighs about 227 grams. When a recipe says "2 cups," what ends up in your bowl depends entirely on what you're measuring and how you scoop it.
This is where things go wrong. Volume measurements assume a consistent density, but flour density changes based on humidity, how long the bag has been open, whether you sifted it, and whether you scooped or spooned it. Two bakers following the same recipe with cups can end up with flour amounts that differ by 15-20%.
Why Grams Work Better
A gram is a gram. It doesn't matter if the flour is packed or fluffy, humid or dry. If your recipe says 250 grams of flour, you put 250 grams on the scale and you're done. Every baker who follows that recipe gets the same amount of flour, every time.
This is why professional bakeries measure by weight. It's why European recipes almost always use grams. And it's why the most reliable baking books published in the last decade include gram measurements alongside cups.
When Cups Are Fine
Not everything needs the precision of a scale. Here's where cups work well enough:
- Liquids like water and milk — they're consistent in density (1 cup of water is always about 237 grams)
- Recipes that are forgiving, like soups, stews, or smoothies
- Small amounts of add-ins like chocolate chips or chopped nuts, where exact quantities don't affect the structure
When You Need a Scale
Use grams whenever the ingredient amount directly affects the chemistry of your bake:
- Flour — always. The difference between 125g and 150g per cup is the difference between a light muffin and a doorstop.
- Sugar — especially when making meringues, caramels, or candy where ratios to liquid matter
- Butter — for pastry doughs where the fat-to-flour ratio determines flakiness
- Leaveners — baking powder and baking soda are potent. Even a few extra grams can cause metallic flavors or over-rising followed by collapse.
Converting Between Cups and Grams
If you're working from a recipe that only uses cups, you'll need ingredient-specific conversions. Here are some of the most common ones:
- All-purpose flour: 1 cup = 125g
- Granulated sugar: 1 cup = 200g
- Brown sugar (packed): 1 cup = 220g
- Butter: 1 cup = 227g
- Powdered sugar: 1 cup = 120g
- Cocoa powder: 1 cup = 86g
Notice how different these numbers are. That's exactly the problem with cups — a "cup" of one ingredient has nothing in common with a "cup" of another, except the volume of the container.
Making the Switch
You don't have to go all-metric overnight. Start by buying a kitchen scale and weighing your flour the next time you bake. Compare the result to what your cup measurement gives you. Most people are surprised by how much extra flour they've been adding. Once you see the difference on the scale, it's hard to go back to cups.