You need 0.89 cups (about 7/8 cup) of cornstarch for 100 g. The calculation is 100 g ÷ 112 g per cup = 0.89 cups, using the King Arthur Baking figure for cornstarch measured spooned and levelled. All conversions on this page are approximate, and a kitchen scale is still the most reliable tool when accuracy matters. Below are the tables for every common weight, worked examples from everyday cooking, and guidance on storage and measuring technique.
About cornstarch
Fine white starch from corn; a powerful thickener with no flavour of its own. Thickening sauces, gravies and custards; lightening cakes. Airtight container, cool and dry, indefinitely. That background matters for converting, because how an ingredient is stored and handled changes how it packs into a cup. A bag that has sat open in a humid kitchen weighs differently from a freshly opened one, and a cook who scoops straight from the bag will pack more into the cup than a cook who spoons it in lightly. Knowing the ingredient helps you judge when the table figure is close enough and when to reach for the scale instead. For baking with flour, the cup weight of 112 g is the anchor: every number on this page is that figure divided or multiplied, never a separate guess.
100 g of cornstarch in cups — conversion table
One cup of cornstarch weighs 112 g (spooned and levelled, King Arthur Baking). Divide any weight in grams by 112 to get cups. The table below does that division for the weights cooks most often meet, from a small 25 g spoonful up to 500 g. All cup figures are approximate.
| Grams | Cups (approx.) | Nearest kitchen measure |
|---|---|---|
| 25 g | 0.22 | about 1/4 cups |
| 50 g | 0.45 | about 1/2 cups |
| 75 g | 0.67 | about 2/3 cups |
| 100 g | 0.89 | about 7/8 cups <-- this page |
| 125 g | 1.12 | about 1 1/8 cups |
| 150 g | 1.34 | about 1 1/3 cups |
| 200 g | 1.79 | about 1 3/4 cups |
| 250 g | 2.23 | about 2 1/4 cups |
| 300 g | 2.68 | about 2 2/3 cups |
| 400 g | 3.57 | about 3 5/8 cups |
| 500 g | 4.46 | about 4 1/2 cups |
Two things are worth noticing in that table. First, the headline row is the one this page is built around: 100 g is 0.89 cups. Second, the relationship is linear, so doubling the grams doubles the cups and halving the grams halves them. That linearity is what makes the table safe to interpolate: if your recipe calls for 175 g, the answer sits halfway between the 150 g and 200 g rows.
Cups of cornstarch back to grams
Sometimes the recipe is written in cups and the scale is the only tool on the bench. Multiply the cups by 112 g to get grams.
| Cups | Grams (approx.) |
|---|---|
| 1/4 cup | 28 g |
| 1/3 cup | 37 g |
| 1/2 cup | 56 g |
| 2/3 cup | 75 g |
| 3/4 cup | 84 g |
| 1 cup | 112 g |
| 1 1/2 cups | 168 g |
| 2 cups | 224 g |
That reverse table is the one to use when a recipe says “one cup of cornstarch” and you would rather weigh it. Weighing removes the packing question entirely, which is why most professional bakers and many recipe developers now write grams first and cups second.
Worked examples
Adjusting a recipe that went wrong
If a previous batch came out too dry or too dense, the cup conversion is a good place to look. A cook who scooped cornstarch straight from the bag may have used well over 112 g per cup, so a recipe that asked for 3 cups could have contained 386 g or more instead of 336 g. Weighing the next batch at 336 g for 3 cups is the simplest fix, and it costs nothing but a minute on the scale.
Shopping and portion planning
Planning a week of cooking is easier in grams. If a dish needs 3 cups of cornstarch and you will make it twice, buy at least 672 g. Working backwards from the cup weight stops the common mistake of buying a small packet that looks generous in the shop and runs out halfway through the second batch, and the grams-to-cups table above makes the check take seconds.
A recipe that calls for cups
A recipe asks for 3 cups of cornstarch. Multiply by the cup weight: 3 × 112 g = 336 g. Weigh 336 g on the scale and you have the recipe amount exactly, with no packing guesswork. This is the most common direction for cooks who own a scale but are following a cup-based recipe, and it is the direction where weighing pays off most, because a scooped cup can easily run 10 to 15 percent heavy.
Method and source
The cup weight used on this page is 112 g for one US cup of cornstarch, measured spooned and levelled, from King Arthur Baking. The method matters as much as the number. Spooned and levelled means the ingredient is transferred into the cup in the way the source describes, then levelled with a straight edge, and any other technique will give a different weight. A cook who scoops directly from the bag compresses the ingredient and can add a tenth or more to the weight, while a cook who sifts first adds air and takes weight away. That is why two honest sources can disagree about a cup weight without either being wrong: they measured differently. All results on this page are approximate. Use them confidently for everyday cooking, and verify with a kitchen scale when the dish depends on precision, when you are scaling a recipe up for a crowd, or when you are developing a recipe other people will follow. A scale costs little, lasts for years, and removes the single biggest source of variation in cup conversions.
Scaling recipes with cornstarch
Scaling a recipe is where grams earn their keep. Doubling by cups means filling the cup twice, and the second cup is rarely packed the same as the first, so the doubled recipe can drift by a noticeable amount. Doubling by grams is exact: twice 336 g is 672 g, with no judgement involved. Halving works the same way, and it is safer in grams because a half cup is a small measure that is easy to misjudge. When you scale, scale everything by weight, not just the cornstarch, or the proportions will shift and the result will change in ways that are hard to diagnose. Keep a note of the scaled grams on the recipe so the next cook does not have to convert twice, and if a scaled bake fails, check the largest ingredient first, because the biggest weight carries the biggest absolute error.
Frequently asked questions
How many cups is the headline amount?
Use the division on this page: the headline weight divided by 112 g per cup. That is the figure in the first paragraph, rounded to two decimals, and it is approximate.
Can I use this conversion for a different brand?
Yes, as a starting point. Brands vary slightly in grind, moisture, and packing, so a cup of one brand may weigh a gram or two more or less than another. If your bake is sensitive, weigh the first batch and note your own brand's figure for next time.
Does temperature change the conversion?
For dry cornstarch the effect is small, but for fats and liquids it matters. A solid fat packs differently from a melted one, and a cold liquid is slightly denser than a warm one. Measure fats in the state the recipe expects, and weigh them when the amount is large.
Is the conversion exact?
No. Cup weights are approximate because cornstarch settles, packs, and varies by brand and humidity. The figures here come from King Arthur Baking and are rounded to two decimal places, so treat them as a reliable guide rather than a laboratory measurement, and weigh with a kitchen scale whenever the recipe depends on precision.
Why do different websites give different answers?
Because a cup is a volume and cornstarch does not always fill it the same way. Spooning versus scooping, sifting, humidity, and brand all shift the weight, so sources disagree by a few grams. We use one named source, King Arthur Baking, for every figure on this page so the numbers stay consistent with each other.