Best Cornstarch Substitutes (With Ratios)
The best cornstarch substitute for thickening sauces, gravies and stir-fries is all-purpose flour: use 2 Tbsp (16 g) flour for every 1 Tbsp (8 g) cornstarch and simmer for 2–3 minutes to cook out the raw taste. For a clear, glossy result, use arrowroot or potato starch 1:1 instead.
Cornstarch substitutes and ratios
| Substitute | Amount per 1 Tbsp cornstarch | Best for | Why it works |
|---|---|---|---|
| All-purpose flour | 2 Tbsp | Gravy, stews, cream sauces | About 70–75% starch, so you need double |
| Arrowroot | 1 Tbsp | Fruit sauces, glazes, Asian-style sauces | Pure starch; thickens clear at lower heat |
| Potato starch | 1 Tbsp | Soups, gravies, crispy frying coatings | Large granules thicken fast at lower temperature |
| Tapioca starch | 2 Tbsp | Pie fillings, sauces you'll freeze | Glossy, freezes well, slightly stretchy |
| Rice flour | 2 Tbsp | Gluten-free gravies, soups | Fine starch with mild flavour |
| Xanthan gum | 1/4 tsp | Low-carb sauces, dressings | Gum thickens without heat; a tiny amount goes far |
The science of starch thickeners
Starch thickens through gelatinization. Raw starch granules soak up hot water, swell to many times their size and release long amylose and amylopectin molecules that tangle and trap liquid. Cornstarch thickens fully close to a boil, around 95 °C / 203 °F.
Each starch behaves a little differently:
- Flour contains protein and fibre alongside its starch, which is why you need twice as much and why the sauce turns cloudy. Its starch is also less concentrated, so it needs a few minutes of simmering to lose its raw, pasty flavour.
- Root starches (arrowroot, potato, tapioca) gelatinize at lower temperatures and give a clearer gel. They're less sturdy, so long boiling or vigorous stirring breaks them down.
- Xanthan gum isn't a starch at all. It's a microbial gum that thickens cold and hot liquids, so stir it in gradually or blend it to avoid clumps.
Always mix any starch with cold liquid first to make a slurry, then whisk it into the hot pot. Dropped straight into hot liquid, the outsides of the granules gel instantly and lock dry powder inside as lumps.
When not to swap
- Arrowroot with dairy. It turns slimy in milk or cream sauces; use flour or cornstarch.
- Flour in clear glazes or fruit fillings. It turns them cloudy and dull.
- Cornstarch in baking recipes. In shortbread or homemade cake flour, cornstarch's job is to lower protein. Flour can't do that, so use arrowroot or potato starch.
- Tapioca in large amounts. Past about 2 Tbsp per cup of liquid it becomes stringy and gummy.
- Very acidic sauces. Long cooking with acid weakens all starches. Add the thickener near the end.
Questions
Is flour or arrowroot better than cornstarch?
Arrowroot gives a clearer, glossier sauce and works at lower heat, but turns slimy with dairy. Flour is cheaper and stable, but needs twice as much and makes an opaque sauce.
Can I use flour instead of cornstarch for frying?
Yes, but the coating will be less crisp. A mix of half flour and half potato starch gets closest to a cornstarch crust.
Why did my arrowroot sauce get thin again?
Arrowroot breaks down if it is boiled for long or stirred hard after thickening. Add it at the end, bring it just to a simmer and take it off the heat.
Is cornstarch the same as cornflour?
In the UK and Australia, 'cornflour' means cornstarch. In North America, corn flour is finely ground whole corn, which does not thicken the same way.