Cornstarch:
Grams to Cups
By Stefan Ulrich · Last updated
Cornstarch weighs 128 grams per cup — close to all-purpose flour but slightly heavier due to its finer, denser particle structure. As a thickening agent, cornstarch is used in tablespoon quantities, making accurate small-scale measurement essential.
How much Cornstarch weighs at each cup measure.
Convert Cornstarch
1 cup = 128 grams
= — grams
= — cups
Quick reference
Measurement Table
| Cups | Grams | Ounces |
|---|---|---|
| 1 tsp | 3 g | 0.11 oz |
| 1 tbsp | 8 g | 0.28 oz |
| ⅛ cup | 16 g | 0.56 oz |
| ¼ cup | 32 g | 1.13 oz |
| ⅓ cup | 43 g | 1.52 oz |
| ½ cup | 64 g | 2.26 oz |
| ⅔ cup | 85 g | 3.00 oz |
| ¾ cup | 96 g | 3.39 oz |
| 1 cup | 128 g | 4.51 oz |
| 1¼ cups | 160 g | 5.64 oz |
| 1½ cups | 192 g | 6.77 oz |
| 2 cups | 256 g | 9.03 oz |
| 3 cups | 384 g | 13.54 oz |
About Cornstarch
Most recipes use cornstarch by the tablespoon: 1 tablespoon = 8 grams, 2 tablespoons = 16 grams. For pie fillings, sauces, and puddings, a 1–2 gram variance in cornstarch can noticeably affect the final consistency — too much and you get a gluey, rubbery texture; too little and your filling won't set.
Cornstarch is used as a thickening agent because its tightly bound starch granules absorb water and swell dramatically when heated, a process called gelatinization. It has roughly twice the thickening power of all-purpose flour — so 1 tablespoon cornstarch replaces 2 tablespoons flour for thickening.
For tender baked goods, adding 2 tablespoons of cornstarch per cup of all-purpose flour reduces the effective protein content, approximating cake flour. This substitution works well when you don't have cake flour on hand.
Cornstarch should always be mixed with a cold liquid (a slurry) before adding to hot liquids — adding it directly to hot liquid creates stubborn lumps.
Tips for measuring Cornstarch
- 2 tbsp (16 g) cornstarch replaces ¼ cup (30 g) flour for thickening.
- Make 'cake flour': 1 cup AP flour minus 2 tbsp, plus 2 tbsp cornstarch.
- Always make a cold slurry first — never add cornstarch to hot liquid directly.
- Arrowroot substitution: 1:1 by weight, but doesn't hold up to prolonged cooking.
- For pie fillings, simmer the thickened mixture briefly to remove the raw starch flavor and get a glossy finish.
- Cornstarch breaks down if it is kept at a hard boil for too long, so stop as soon as the filling turns glossy.
Common mistakes
- Adding cornstarch directly to hot liquid — results in irreversible lumps
- Overheating cornstarch-thickened sauce — it breaks down and re-liquefies above 200°F
- Using cornstarch as a 1:1 swap for flour in cakes or cookies without adjusting the ratio.
Frequently Asked Questions
- How many grams in a cup of Cornstarch?
- 1 cup of Cornstarch weighs 128 grams — the standard used in most American recipes. Use the converter above for any other amount.
- How many grams is 1 tablespoon of Cornstarch?
- 1 tablespoon of Cornstarch weighs about 8 grams. The full table above lists every common cup fraction.
- What's the most common mistake when measuring Cornstarch?
- Adding cornstarch directly to hot liquid — results in irreversible lumps. Weighing on a kitchen scale avoids it entirely.
- Does Cornstarch need to be levelled in the cup?
- Yes — spoon cornstarch in and sweep a straight edge across the top. Scooping or tapping compacts it and changes the weight.
Related ingredients
All-Purpose Flour
1 cup = 120 g
Cake Flour
1 cup = 100 g
Granulated Sugar
1 cup = 200 g
Shredded Coconut
1 cup = 85 g
Table Salt
1 cup = 288 g
Vanilla Extract
1 cup = 208 g
Raisins
1 cup = 165 g
Poppy Seeds
1 cup = 140 g
Sesame Seeds
1 cup = 144 g
Pumpkin Puree (Canned)
1 cup = 245 g
Lemon Juice
1 cup = 244 g
Applesauce
1 cup = 244 g
Cream of Tartar
1 cup = 150 g
Breadcrumbs (Dry)
1 cup = 108 g
White Chocolate Chips
1 cup = 170 g
Dark Chocolate Chips
1 cup = 170 g