Substitute Flour for Cornstarch: The Right Ratio

To substitute flour for cornstarch, use twice as much flour by volume: 2 tablespoons (about 16 g) of all-purpose flour for every 1 tablespoon (8 g) of cornstarch. This simple flour-thickened sauce shows how to apply the ratio, while the instructions explain how to adapt it to gravy, soups, stews, and other recipes.

Ingredients

4 tablespoons (32 g) all-purpose flour
2 cups (475 ml) stock, divided: ½ cup (120 ml) cold and 1½ cups (355 ml) warm; chicken, beef, or vegetable stock all work
¼ teaspoon (1.5 g) fine salt, or to taste
⅛ teaspoon (0.3 g) ground black pepper, or to taste

Instructions

Start with the conversion. For this recipe, 4 tablespoons of flour replace 2 tablespoons of cornstarch and thicken 2 cups of stock. That is the useful baseline: use 2 tablespoons of flour for each 1 tablespoon of cornstarch in a recipe, then adjust slightly for the thickness you want. Measure flour with a spoon and level it rather than packing it into the spoon.
Warm the stock. Heat 1½ cups of stock in a small saucepan over medium heat until steaming but not boiling, about 2 minutes. Keep the remaining ½ cup cold; cold liquid helps you make a smooth flour slurry before it meets the hot stock.
Whisk the slurry. Put the flour in a medium bowl. Add the cold stock a little at a time, whisking continuously, until you have a smooth, pourable mixture with no dry pockets. Scrape the bottom and sides of the bowl. If you spot lumps, press them against the bowl with the whisk or pass the slurry through a fine strainer.
Combine gradually. Whisk the warm stock as you slowly pour in the slurry. Continue whisking until the mixture is even. Pouring the flour mixture in all at once can create lumps, especially if the stock is very hot.
Simmer until thickened. Bring the sauce to a gentle simmer over medium heat, stirring frequently, and cook for 6 minutes. It should coat the back of a spoon and become less floury in flavor as it cooks. Avoid a vigorous boil; if it thickens too much, whisk in stock a tablespoon at a time.
Season and serve. Stir in the salt and pepper, taste, and adjust the seasoning. Use the sauce right away, or keep it warm over low heat while stirring occasionally. It will thicken a little more as it stands.

Tips

Keep the ratio tied to the original amount. If a recipe calls for 1 tablespoon of cornstarch, begin with 2 tablespoons of flour. For 2 teaspoons of cornstarch, use 4 teaspoons of flour. This is a starting conversion, not a guarantee that every sauce will set to exactly the same consistency: the amount of liquid, cooking time, and other ingredients all affect thickness. If you know the original recipe makes a very thick filling, you may need a little more flour; if it is a light pan sauce, start with less and add only if needed.
Do not add flour dry to a hot pot. Flour clumps when its surface gets wet before it can disperse, leaving small doughy lumps in the sauce. Mix it with cold liquid first, or make a roux by cooking it with fat. A fork can break up a few tiny lumps, but whisking a smooth slurry before it reaches the pan is more reliable.
Give flour time to cook. Cornstarch can thicken quickly once heated, but flour usually needs several minutes of gentle simmering to lose its raw, pasty taste. Stir as it cooks and keep the heat moderate. If your recipe has delicate ingredients that should not simmer for long, cook the flour separately in butter or oil before adding the liquid.
Expect a different finish. Flour-thickened sauces tend to look more opaque and have a softer, heartier texture than sauces thickened with cornstarch, which are often clearer and glossier. Flour contains gluten unless you choose a gluten-free blend, so it is not a suitable substitute for someone who needs to avoid gluten.

Serving Suggestions

Serve this stock sauce over mashed potatoes, roasted vegetables, biscuits, rice, or sliced roast meat. It is intentionally mild, so it can take on the flavor of whatever it accompanies. For a quick pan sauce, scrape browned bits from the pan with a splash of stock, add the flour slurry, then whisk in the remaining warm stock. Taste before adding salt because pan drippings and prepared stock can already be salty.

The same flour-to-cornstarch conversion works in many savory dishes, but the method may need to change. In a stew, whisk flour with a little cold broth before stirring it into the pot, then simmer long enough to cook away the raw taste. For a smooth soup, take a cup of broth from the pot, cool it briefly, whisk in the flour, and return that mixture to the simmering soup. Add thickener gradually: you can always add more, while thinning an overly thick sauce changes its seasoning and flavor.

Variations

Make a roux for richer gravy. Melt 2 tablespoons (28 g) butter in a saucepan, whisk in 2 tablespoons (16 g) flour, and cook for 1 to 2 minutes before gradually adding 2 cups (475 ml) stock. This still follows the flour-for-cornstarch conversion when replacing 1 tablespoon of cornstarch, but the fat-and-flour base adds richness and a slightly toasted flavor. Stir constantly so the flour cooks evenly without browning more than you intend.

Use pan drippings. Replace some or all of the butter in the roux with strained meat drippings. Measure the fat first; if you have less than 2 tablespoons, top it up with butter or oil. Whisk in the flour, cook briefly, then add stock. For a smoother result, strain the finished gravy. The drippings will make the sauce more savory, so season only after tasting.

Choose a gluten-free flour blend. A cup-for-cup gluten-free blend can thicken a sauce, but blends vary and may contain starches or gums that change how quickly they thicken. Start with the same volume as the all-purpose flour amount, simmer, and assess the texture before adding more. Avoid assuming that every single gluten-free flour, such as almond or coconut flour, will behave like wheat flour; some add a noticeable flavor or do not make a smooth sauce.

Adjust the thickness for the dish. For a pourable sauce, begin with about 1½ tablespoons (12 g) flour per cup (240 ml) liquid in place of ¾ tablespoon (about 6 g) cornstarch. For a thicker gravy or filling, use the full 2 tablespoons (16 g) flour per cup (240 ml) liquid for each 1 tablespoon (8 g) cornstarch being replaced. Make changes in small increments and simmer before deciding whether the sauce needs more thickener.

Storage and Reheating

Cool leftover sauce promptly and refrigerate it within 2 hours in a covered, shallow container. It keeps for 3 to 4 days in the refrigerator. Flour-thickened sauces can form a skin or become quite thick as they chill; press food-safe wrap against the surface before covering if you want to reduce skin formation. Do not leave the sauce at room temperature for extended storage.

Reheat the sauce gently in a saucepan over low to medium-low heat, whisking often. Add stock or water a tablespoon at a time if it has become too thick. Heat leftovers to 165°F (74°C), stirring so the temperature is even, and avoid a hard boil that can make the texture less smooth. A microwave also works: use short intervals, stir thoroughly between them, and continue until steaming hot throughout. Freeze the sauce in a sealed freezer-safe container for up to 2 months for best quality. Thaw it in the refrigerator, then whisk while reheating; some separation may occur, but gentle stirring often brings it back together.

Frequently Asked Questions

What is the exact ratio for substituting flour for cornstarch?
Use 2 tablespoons (about 16 g) of all-purpose flour for every 1 tablespoon (about 8 g) of cornstarch. Flour generally has less thickening power by volume, which is why you need twice as much. For a recipe with 2 tablespoons of cornstarch, start with 4 tablespoons of flour, then evaluate the finished texture.

Can I put flour directly into a sauce that is already cooking?
It is better not to sprinkle dry flour straight into hot liquid because it can form lumps that are difficult to whisk out. Blend the flour with cold water or broth first, or cook it with butter or oil as a roux. Add either mixture gradually while stirring, then simmer the sauce for several minutes so the flour cooks through.

Can I use this substitution in pie filling or fruit sauce?
Often, but the result will be more opaque and may feel less glossy than a cornstarch-thickened filling. Flour can also make delicate fruit flavors seem less bright. Use the doubled amount as a starting point, follow the recipe’s cooking method where practical, and allow the filling to cook sufficiently for the flour to lose its raw taste. For a clear, shiny finish, flour is not the closest match.

Will flour thicken a cold sauce or dressing?
No. Flour needs to be heated in liquid to thicken properly, so it is not a direct choice for a dressing or dessert sauce that must remain cold. Use an ingredient intended for cold thickening, or choose a different recipe. If the original cornstarch is cooked into a mixture that is later chilled, flour may work, but the finished texture can be softer and less clear.

Can I use self-rising flour instead of all-purpose flour?
All-purpose flour is the better choice because self-rising flour contains added leavening and salt. Those additions are unnecessary in a sauce and can affect its taste. If self-rising flour is all you have, it may thicken a savory sauce, but skip or reduce added salt and use it only when a small change in flavor and texture is acceptable.

Why is my flour-thickened sauce still thin?
It may need more simmering time, or the flour may not have been measured in the right proportion to the liquid. Let it gently simmer for another minute or two, stirring, before adjusting. If it remains too thin, whisk a small amount of flour into cold water in a separate bowl and add it gradually. Do not add a spoonful of dry flour to the pot; that is likely to create lumps.

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