Cornstarch substitutes, and the ratio each one needs
Use twice as much plain flour, or half as much arrowroot. The ratios matter more than the choice, and one common swap fails completely in acidic sauces.
How they compare, per 100 g
Most substitute guides tell you what works and stop there. If you are choosing partly on macros, here are the numbers side by side.
| Per 100 g | kcal | Protein | Carbs | Fat |
|---|---|---|---|---|
| Cornstarch | 381 | 0.3 g | 91 g | 0.1 g |
| Plain flour | 364 | 10.3 g | 76 g | 1 g |
| Arrowroot | 357 | 0.3 g | 88 g | 0.1 g |
| Tapioca starch | 358 | 0.2 g | 89 g | 0 g |
| Potato starch | 333 | 0.1 g | 83 g | 0.1 g |
| Rice flour | 366 | 6 g | 80 g | 1.4 g |
| Ground flaxseed | 534 | 18.3 g | 29 g | 42 g |
Typical values, rounded. Brands vary, so treat these as estimates for comparing options rather than exact figures.
Every option, and when to use it
ReciPop picks one swap because it is optimising for your macro goal. Cooking is broader than that, so here is the full list including the ones the app does not reach for.
| Use | How much | Best for |
|---|---|---|
| Plain flour | 2 tbsp flour per 1 tbsp cornstarch | gravies, stews, and roux-based sauces Watch out: cook it out for a couple of minutes or the sauce tastes raw and pasty |
| Arrowroot | 2 tsp arrowroot per 1 tbsp cornstarch | clear sauces, fruit fillings, and anything acidic Watch out: goes slimy with dairy, so keep it out of cream sauces |
| Tapioca starch | 2 tbsp tapioca per 1 tbsp cornstarch | pies, fruit fillings, and anything you will freeze Watch out: stringy if you boil it hard |
| Potato starch | 1:1 | sauces and soups, and it is the easiest straight swap Watch out: thins out if it boils, so add it near the end |
| Rice flour | 2 tbsp rice flour per 1 tbsp cornstarch | clear Asian-style sauces and frying batters |
| Ground flaxseed | 1 tbsp flax per 1 tbsp cornstarch | rustic soups and stews where a little texture is fine Watch out: adds a nutty taste and a slightly gritty body |
| Reduce the liquid instead | no substitute at all | sauces where you have time to simmer Watch out: concentrates the salt as well as the flavour, so season at the end |
Ratios matter more than the choice
Almost any starch will thicken a sauce. Getting the quantity wrong is what ruins the dish, and the quantities are not intuitive.
Cornstarch is close to pure starch. Flour is only about three quarters starch, with protein and fibre taking up the rest, so it needs roughly double. Arrowroot is more concentrated, so it needs about two thirds. Swap one for another at 1:1 and you will get either a watery sauce or wallpaper paste.
Everything below replaces 1 tbsp of cornstarch.
| Substitute | Use this much | Why the ratio differs |
|---|---|---|
| Potato starch | 1 tbsp | Almost pure starch, like cornstarch, so it swaps straight across |
| Arrowroot | 2 tsp | More concentrated, so you need about two thirds |
| Plain flour | 2 tbsp | Only three quarters starch, the rest is protein and fibre |
| Tapioca starch | 2 tbsp | Coarser and weaker by volume |
| Rice flour | 2 tbsp | Similar strength to flour, but sets clearer |
The failure nobody warns you about
Cornstarch loses its thickening power in acid. A lemon sauce, a tomato-heavy braise, a fruit filling: all of them can turn watery after cornstarch seemed to work, because the acid breaks down the starch as it sits.
Long cooking does the same thing. Once a cornstarch-thickened sauce has been at a hard boil for a while, it starts to thin again.
Arrowroot is the fix for both. It tolerates acid, sets clear rather than cloudy, and holds. The trade is that arrowroot turns unpleasantly slimy with dairy, so it is the wrong choice for a cream sauce and the right one for a fruit glaze.
Which to use for what
Gravy and stew: plain flour. It is already in the kitchen, it suits an opaque sauce, and the slight flavour it adds is welcome. Cook it out.
Clear or acidic sauces, fruit fillings: arrowroot.
Pies and anything freezing: tapioca. Cornstarch-thickened fillings weep after freezing and thawing. Tapioca does not.
Frying: rice flour or potato starch. Both give a crisper coating than flour, and rice flour is arguably better than cornstarch for this.
When you have time: nothing. Simmer it down. Reduction thickens and concentrates flavour at once, and costs you no ingredients. Season at the end, because it concentrates salt too.
What it costs you
Starches are close to interchangeable on macros. Per 100 g they all land between roughly 333 and 381 kcal, almost entirely carbohydrate.
The two exceptions are worth knowing. Plain flour brings about 10 g of protein per 100 g against cornstarch’s 0.3, so it is marginally more nutritious. Ground flaxseed is a different thing entirely at roughly 534 kcal, 18 g protein and 42 g fat, so it is a fibre-and-fat addition that happens to thicken rather than a like-for-like swap.
In practice you use a tablespoon or two across a whole dish, so none of this moves a per-serving number much. It is worth knowing, not worth worrying about.
Values are typical figures, rounded, and vary by brand.
Common questions
Plain flour is the most likely thing to be in the cupboard. Use twice as much as the cornstarch called for, and let it cook for a couple of minutes so it does not taste raw. Potato starch is the closest straight swap at 1:1 if you have it.
Two tablespoons. Cornstarch is close to pure starch while flour is only about three quarters starch, with protein making up much of the rest, so you need roughly double the quantity to get the same thickening.
Arrowroot. Cornstarch loses thickening power in acid and with long cooking, which is why lemon or tomato sauces thinned with it can go watery. Arrowroot holds up, sets clear, and needs only about two teaspoons per tablespoon of cornstarch.
Rice flour is the best of them and arguably better than cornstarch for a crisp coating. Potato starch also fries well. Plain flour gives a softer, more bread-like crust rather than a shattering one.
Often not. Simmering a sauce uncovered reduces the water and thickens it with no starch involved, which also concentrates the flavour. The catch is that it concentrates salt too, so hold back on seasoning until the end.