There are about 8.9 cups in a kilogram of cornstarch — approximately, because the figure depends on how the flour is measured. One US cup of cornstarch weighs 112 g spooned and levelled, so 1,000 g divided by 112 g gives about 8.93 cups. That is the short answer, and the rest of this guide explains where the number comes from, how much it moves when the measuring method changes, and how to use it in real recipes — from a single cake to a bakery-scale bake.

Cornstarch is not really a flour at all — it is a pure starch, a thickener — but it lives in the flour aisle and it is measured the same way. A cup weighs about 112 g, so a kilogram gives about 8.9 cups. That is a huge amount for an ingredient used by the tablespoon: a kilogram of cornstarch is a lifetime supply for most kitchens, and the number matters mainly for buying in bulk or for scaling a commercial recipe.

Every figure on this page is labelled approximate, and for good reason: cup measurements vary with packing, moisture and the size of the pieces. When a recipe depends on the amount — a cake, a loaf of bread, a jam that has to set — weigh the ingredient on a kitchen scale instead of trusting the cup. The scale is the only measuring tool that does not care how you filled the cup.

The conversion at a glance

One cup of cornstarch weighs 112 g spooned and levelled. A kilogram is 1,000 g, so the arithmetic is 1,000 ÷ 112 = about 8.93 cups. The table below gives the cup equivalents for the amounts you are most likely to meet, whether you are scaling a recipe up or working out how far a bag will go. All figures are approximate, and all of them use the same 112 g per cup.

Amount Grams Cups (approx.) Tablespoons (approx.)
100 g 100 g 0.9 cups 14 tbsp
250 g 250 g 2.2 cups 36 tbsp
500 g 500 g 4.5 cups 71 tbsp
1 kg 1000 g 8.9 cups 143 tbsp
2 kg 2000 g 17.9 cups 286 tbsp
5 kg 5000 g 44.6 cups 714 tbsp

A single tablespoon of cornstarch weighs about 7.0 g, and a teaspoon about 2.3 g — useful when a recipe calls for a spoonful rather than a cup. Note that a kilogram is about 2.2 lb, so the same kilogram works out to about 8.9 cups by the pound route as well: the two routes agree, because they are the same arithmetic with the same density. If you buy flour in pounds rather than kilograms, one pound of cornstarch is about 4.0 cups.

Worked examples

A kilogram of cornstarch and a year of sauces

Cornstarch thickens sauces by the tablespoon: a sauce for four needs about 1 tablespoon, about 8 g, mixed with cold water into a slurry and stirred into the simmering sauce. A kilogram gives about 8.9 cups, or about 125 tablespoons — enough for two years of weekly sauces. Mix the cornstarch with cold water first: added straight to a hot sauce, it forms lumps that never dissolve, while a slurry disperses instantly and thickens smoothly.

A fruit pie for a celebration

Fruit pies are the baking use for cornstarch. A pie for eight needs about a quarter cup, about 28 g, tossed with the fruit and sugar to thicken the juices as the pie bakes. A kilogram covers 35 pies. Toss the cornstarch with the fruit before filling the pie: cornstarch added on top sits in a layer, while cornstarch mixed through the fruit thickens evenly and the pie slices cleanly instead of running.

A light sponge cake

Sponge cakes use cornstarch to lighten the crumb: replacing 2 tablespoons of flour per cup with cornstarch gives a more tender cake. A cake using 3 cups of flour needs 6 tablespoons of cornstarch, about 45 g, and a kilogram covers 22 cakes. The cornstarch lowers the protein content of the flour, which is the same trick that makes cake flour tender — and it is why a sponge made with a little cornstarch is lighter than one made with flour alone.

How the figure is measured

The headline figure comes from the CookScale ingredient table, which lists cornstarch at 112 g per US cup (236.6 ml), spooned and levelled, sourced from King Arthur Baking with high confidence. Fine white starch from corn; a powerful thickener with no flavour of its own. The table's uses for cornstarch are: Thickening sauces, gravies and custards; lightening cakes.

The method matters more than most people realise. Spooned and levelled is the standard for this ingredient, and a different method gives a different weight: scooping instead of spooning compresses dry ingredients and can add 10–20% to the weight of a cup, while packing a sticky ingredient can add even more. That is why this guide states the method alongside every figure, and why the headline number is always labelled approximate. If you measure differently from the stated method, expect a different result — and if the recipe matters, weigh the ingredient instead.

One practical consequence: never convert in the wrong direction by accident. To go from cups to grams, multiply the cups by 112. To go from grams to cups, divide the grams by 112. To go from kilograms to cups, divide the grams (1,000 per kilogram) by 112. Keep the 112 g figure in mind and the rest is simple division — but always check the result against a scale when the bake depends on it.

Practical guidance

The mistake is adding cornstarch straight to a hot liquid. Cornstarch granules swell and burst on contact with heat, and granules added dry to a hot sauce form lumps with dry centres that never dissolve. Always mix cornstarch with a little cold water first to make a smooth slurry, then stir the slurry into the simmering liquid. The sauce thickens within a minute of boiling — and if you boil it for too long, the starch breaks down and the sauce thins again.

Storage: Airtight container, cool and dry, indefinitely. Weighing the ingredient before you store it, and writing the weight on the container, saves a conversion later: a tub labelled '450 g' tells you instantly that it holds about 8.9 cups, without any measuring at all.

When you do not have a scale: use the cup, but use it carefully. Spoon the ingredient into a dry measuring cup — never scoop from the bag — and level the top with the back of a knife without tapping or shaking the cup. For sticky or wet ingredients, use a liquid measuring jug and read the level at eye height, or lightly oil the cup so the ingredient releases cleanly. Accept that the result will be approximate, and if the recipe is a cake, a loaf or a jam, borrow a scale: it is the single most useful tool in baking, and it costs less than a bag of the flour it measures.

Frequently asked questions

How many cups are in 1 kg of cornstarch?

About 8.9 cups. One cup of cornstarch weighs 112 g spooned and levelled, and a kilogram is 1,000 g, so 1,000 divided by 112 gives about 8.9 cups. A 500 g bag is about 4.5 cups and a 100 g box about 0.9 cups. In practice you will use cornstarch by the tablespoon — one tablespoon weighs about 8 g — so a kilogram is about 125 tablespoons.

How many tablespoons of cornstarch are in a cup?

16 tablespoons. One cup of cornstarch is 16 tablespoons and weighs about 112 g, so one tablespoon weighs about 7 g — usually rounded to 8 g in recipes. A teaspoon weighs about 2–3 g. These are useful figures because cornstarch recipes are almost always written in tablespoons rather than cups.

Can I substitute cornstarch for flour as a thickener?

Yes, but use half as much: 1 tablespoon of cornstarch thickens about as much as 2 tablespoons of flour. Cornstarch gives a clear, glossy sauce, while flour gives an opaque, matte one — so cornstarch suits fruit sauces and stir-fry glazes, and flour suits gravies and béchamel. Cornstarch also thickens at a lower temperature and breaks down if it is boiled for too long.

Should I weigh cornstarch or measure it in cups?

Weigh it whenever the recipe matters. One cup of cornstarch weighs 112 g spooned and levelled, but that figure assumes the stated method — and in practice, cups vary by 10–20% depending on how they are filled. A kitchen scale removes that variation entirely: 112 g is one cup, every time, regardless of who is measuring. Cups are fine for soups, salads and smoothies, where a little more or less makes no difference. For baking, jam, bread and anything where the ratio of ingredients decides the outcome, the scale is the right tool.

How accurate is the about 8.9 cups figure?

It is accurate to about plus or minus half a cup per kilogram, which is roughly the variation you get from different measuring methods and different batches of the ingredient. The figure is calculated from a single sourced density — 112 g per cup from King Arthur Baking, high confidence — and the arithmetic is exact: 1,000 ÷ 112 = 8.93 cups. The uncertainty is not in the maths but in the cup itself: a scooped cup weighs more than a spooned cup, and a packed cup weighs more than a loose one. Treat 8.9 cups as a planning figure and verify with a scale when it matters.

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