Cups vs Grams: Why Baking by Weight Is More Accurate
Reputable baking authorities disagree about what a cup of flour weighs, and the spread is about 17 percent. That is enough to change a cake.
The sources disagree
| Source | Grams per cup of all-purpose flour | Difference from King Arthur |
|---|---|---|
| King Arthur Baking | 120 g | — |
| Google AI Overview (observed August 2026) | 125 g | +4% |
| America's Test Kitchen | 140 g | +17% |
These aren't careless figures. Each comes from a source that bakes seriously and tested its own method. They disagree because they are measuring slightly different things: not flour, but flour as filled into a cup by a particular technique.
Why they disagree
Flour compresses. Dip a measuring cup into a bag and you compact the flour as you go, then compact it further levelling the top. Spoon flour gently into the cup and level it, and you get noticeably less in the same volume. Neither method is wrong. Neither is standardized.
The scoop-and-sweep method generally yields the heaviest cup. The spoon-and-level method yields the lightest. Two sources that test with different methods will report different numbers for the same ingredient, and both can be right.
A weight, by contrast, is a weight. 120 grams of flour is 120 grams regardless of how it got onto the scale.
Which ingredients it actually affects
| Ingredient | How badly measuring affects it | Why |
|---|---|---|
| All-purpose flour | Badly | Compresses when scooped, and it is usually the largest ingredient by volume |
| Powdered sugar | Badly | Clumps and compresses more than granulated |
| Brown sugar | Depends on packing | Recipes assume packed, which is itself imprecise |
| Cocoa powder | Badly | Very low density, so small packing differences move the weight a lot |
| Granulated sugar | Barely | Free-flowing crystals of consistent size |
| Water and milk | Not at all | Liquids fill the cup the same way every time |
| Butter | Not at all | Usually sold in marked sticks or weighed |
The pattern is density and compressibility. Light, powdery ingredients are affected most. Liquids aren't affected at all, which is why the ounces to cups converter can treat fluid measures as a fixed ratio while dry measures need an ingredient.
When it matters and when it doesn't
It matters most where the ratio between ingredients drives the chemistry. Bread dough hydration, pastry, and anything with a tight flour-to-fat or flour-to-liquid balance will show the difference as a texture change. A 17 percent flour error in a cake batter is the difference between tender and dry.
It matters least in cooking that tolerates variation. A stew, a soup, a stir fry, a pot of rice you can check as it goes. Use the cup and move on.
What to do about it
If you have a scale, use it, and take the gram figures from whichever source your recipe came from rather than mixing sources within a recipe. Consistency within one recipe matters more than which chart is right.
If you don't have a scale, use the spoon-and-level method and be aware that recipes written by scoop-and-sweep bakers will come out slightly light. The cups to grams converter uses King Arthur's 120 g figure and says so on the page.
Common questions
How much does a cup of flour weigh?
It depends who you ask, which is the point of this page. King Arthur Baking gives 120 grams, America's Test Kitchen gives 140 grams, and Google's answer box currently shows 125 grams.
Why do the sources disagree?
Because they are measuring flour as filled into a cup by different techniques. Scooping compresses the flour and spooning it in doesn't, so the same cup can hold noticeably different amounts.
Which ingredients are worst affected?
Flour, powdered sugar and cocoa powder, because they are light and compressible. Granulated sugar is barely affected, and liquids such as water and milk aren't affected at all.
Does this matter for every recipe?
No. It matters most where the ratio between ingredients drives the chemistry, such as bread dough and pastry. For a stew or a soup, use the cup and move on.
Related guides
Sources
- Ingredient Weight Chart. King Arthur Baking. Source for the 120 g per cup figure and for the ingredient weights used by this site's cooking converters.
- America's Test Kitchen gives 140 g per cup of all-purpose flour. Reported figure, cited here as a documented point of disagreement rather than as a value this site uses.
- Google AI Overview for the query "cups to grams", observed August 2026, showed 125 g per cup of flour. AI Overview content changes frequently and this figure may no longer be shown.