1 Cup Cornstarch in Grams
1 cup of cornstarch weighs 112 g (spooned and levelled, King Arthur Baking). Fine white starch from corn; a powerful thickener with no flavour of its own. All the figures on this page are approximate conversions based on the King Arthur Baking value, so when a recipe really matters, verify with a kitchen scale.
Why weighing cornstarch beats measuring it in cups
Flour is the ingredient where cup measurements fail most often, and the reason is packing. The same cup of flour can weigh anywhere from 120 g to 142 g depending on whether you scoop it straight from the bag or spoon it in lightly, and that 20 g swing is the difference between a tender cake and a dry one. In a loaf of bread the error is more forgiving, because bread dough can be adjusted by feel, but in a cake or a batch of cookies there is no second chance once the batter is mixed. Weighing flour is the single highest-value habit a home baker can adopt, and it costs nothing more than a basic kitchen scale.
Fine white starch from corn; a powerful thickener with no flavour of its own. It is used for thickening sauces, gravies and custards; lightening cakes. That range of uses is part of why the conversion comes up so often: the same ingredient appears in everyday cooking and in precise baking, and the two situations demand different levels of accuracy.
Cornstarch cups to grams conversion table
| Cups | Grams | Tablespoons (approx.) |
|---|---|---|
| 1/4 cup | 28 g | 1.8 g |
| 1/3 cup | 37.3 g | 2.3 g |
| 1/2 cup | 56 g | 3.5 g |
| 2/3 cup | 74.7 g | 4.7 g |
| 3/4 cup | 84 g | 5.2 g |
| 1 cup | 112 g | 7 g |
| 1 1/2 cups | 168 g | 10.5 g |
| 2 cups | 224 g | 14 g |
| 3 cups | 336 g | 21 g |
| 4 cups | 448 g | 28 g |
The tablespoon column is a bonus for recipes that call for a spoonful or two: one tablespoon of cornstarch weighs about 7 g. Remember that a cup is 16 tablespoons, so the numbers in the table are just the cup weight divided by 16, rounded to one decimal place. For small amounts a scale that reads to the gram is far more reliable than a spoon, because a heaped tablespoon can weigh half as much again as a level one.
How the weight was measured
Spooned and levelled means spooning the ingredient into the measuring cup until it is heaped, then sweeping a straight knife across the top to level it off. Never scoop the cup through the bag or jar, and never tap the cup down, because both pack the ingredient and add weight.
The source for the 112 g figure is King Arthur Baking, and the confidence in the value is high. King Arthur Baking publishes a standard ingredient weight chart that recipe developers use as a reference, and this page follows it exactly rather than averaging across sources, because an average of two different measuring methods is a number that matches nobody's cup.
Worked examples
A sponge cake that calls for 2 cups
A classic sponge asks for 2 cups of cornstarch, which is 224 g. If you scooped those cups from the bag you could easily be adding 260 to 280 g instead, and the extra flour would dry the crumb out and stop the cake rising properly. Weigh 224 g on the scale, and the cake comes out the same every time.
Halving a cookie recipe
Halving a cookie recipe that uses 1 cup of cornstarch means 1/2 cup, which is 56 g. Half-cup measures are notoriously inaccurate with flour because the small cup packs differently, so weighing 56 g is the reliable way to halve a recipe without the cookies turning out cakey or flat.
Doubling a bread dough
Doubling a bread recipe that uses 3 cups of cornstarch means 3 cups, or 336 g. Bread dough is forgiving and can be adjusted by feel, but starting from 336 g means the hydration is right from the first mix, and you are not adding flour by the handful to fix a sticky dough.
When this conversion matters most
This conversion matters most in baking, where flour is the structure of the recipe. In a yeast bread the effect of an extra 20 g is small, because the dough can be adjusted, but in a cake, a sponge or a batch of macarons the same error can be the difference between success and failure. It also matters when you are following a recipe from another country: most of the world bakes in grams, and a cup measure is an American habit. Converting to grams lets you use any recipe, from any source, with the same confidence.
Common mistakes with cornstarch
- Scooping straight from the bag. Pushing the cup into the bag compresses the flour and can add 20 g or more per cup. Spoon the flour into the cup and level it off with a knife instead.
- Skipping the scale for cakes. Cakes and delicate batters have no room for a 20 g error. If you own a scale, weigh the flour even when the recipe gives cups.
- Measuring sifted flour the same as unsifted. Sifting adds air and lightens flour, so a cup of sifted flour weighs less than a cup of unsifted flour. Measure before sifting unless the recipe says otherwise.
- Using a liquid measuring jug for flour. Jugs are for pouring, and you cannot level flour in one. Use a dry measuring cup or, better, a scale.
Storage and handling
Airtight container, cool and dry, indefinitely. Keeping cornstarch stored properly also keeps its weight per cup stable: an ingredient that has absorbed moisture from the air weighs more per cup than a dry one, so a sealed container is not just about freshness, it is about measurement accuracy too. If a bag has been open for months in a humid kitchen, the first thing to do before a precise bake is to weigh the ingredient rather than trusting the cup.
Frequently asked questions
How many grams is 1 cup of cornstarch?
1 cup of cornstarch weighs 112 g, measured spooned and levelled according to King Arthur Baking. That is the figure to use when converting a recipe from cups to grams, and it is the value the conversion table on this page is built on.
How do I measure cornstarch without a scale?
Spooned and levelled means spooning the ingredient into the measuring cup until it is heaped, then sweeping a straight knife across the top to level it off. Never scoop the cup through the bag or jar, and never tap the cup down, because both pack the ingredient and add weight. That gives the closest result to 112 g per cup, but it is still an estimate: the honest answer is that a scale is the only way to know the exact weight, and a basic digital kitchen scale costs less than a bag of good flour.
Does cornstarch always weigh the same per cup?
No. Brand, grind, moisture and how settled the container is all shift the weight by a few grams, and for flour the swing can be 20 g or more. The 112 g figure is the standard King Arthur Baking value for cornstarch measured spooned and levelled, and it is the right default, but when a recipe is precise, weigh the ingredient and trust the scale over the cup.
Can I use the same conversion for a different brand of cornstarch?
Yes, as a starting point. The 112 g figure is a standard average for cornstarch, and most brands sit within a few grams of it. If you bake with one brand all the time, weigh one cup of it once and note the number on the bag, and you will have a conversion tuned to your own kitchen.
How should I store cornstarch?
Airtight container, cool and dry, indefinitely. Good storage keeps the ingredient fresh and keeps its weight per cup consistent, because moisture absorbed from the air adds grams that the recipe did not ask for.
What is cornstarch used for?
Thickening sauces, gravies and custards; lightening cakes. Fine white starch from corn; a powerful thickener with no flavour of its own.
Related conversions
Use the cups to grams converter or the grams to cups converter for instant answers, or browse the cups to grams hub for the full ingredient list. Related pages: All-Purpose Flour in cups to grams, Cake Flour in cups to grams, Bread Flour in cups to grams. More tools: cups to grams converter, grams to cups converter, flour substitute converter, recipe scaler. See also our disclaimer about approximate conversions.