Learn how to thicken a sauce with two simple ingredients: flour or cornstarch. We have guidelines for using these two ingredients so you'll know how to thicken gravy, sauces, and more in no time. Gluten-free? We've got Test Kitchen tips for substituting cornstarch for flour, too.

Have you ever tried to twirl a bite of pasta that, by the time it reaches your mouth, seems to have no sauce? Or maybe you pour turkey gravy over meat and potatoes only finding it to spread over the entire plate? Then you've experienced the importance of mastering how to thicken sauces. You want to serve up sauces that have the right viscosity to cling to the intended food, not run everywhere. Here are some tips on how to thicken sauce with cornstarch and flour—items likely already in your pantry so you don't have to run to the store.

Thicken Sauce with Flour
Credit: Blaine Moats


How to Thicken Sauce with Flour

When using flour as a thickening agent, be sure to thoroughly mix the water with the flour to prevent lumps. After stirring the combined flour and water into the sauce, cook and stir over medium heat until thickened and bubbly. Heat one minute more to completely cook the flour. To use flour as a thickening agent:

  • Use 2 Tbsp. flour mixed with ¼ cup cold water for each cup of medium-thick sauce.

How to Thicken Sauce with Cornstarch

Thickening a sauce with cornstarch is very similar to using flour, you just need different quantities. Be sure to thoroughly mix the cornstarch and water together, then pour into your sauce. Cook and stir over medium heat until thickened and bubbly. Heat two minutes more in order to completely cook the cornstarch. When using cornstarch as a thickening agent, here's how much you'll need:

  • Use 1 Tbsp. cornstarch mixed with 1 Tbsp. cold water (aka a cornstarch slurry) for each cup of medium-thick sauce.

Test Kitchen Tip: Be careful not to overcook cornstarch-thickened sauces as they can break down when overcooked (the starch loses its thickening properties when cooked too long).

Substituting Cornstarch for Flour as a Gluten-Free Alternative

Whether you ran out of flour or have someone in the family with an allergy restriction and need a gluten-free thickener for your soup recipe, it's important to note cornstarch has twice the thickening power of flour. So if you need to substitute cornstarch in a gravy recipe that calls for ¼ cup (4 Tbsp.) flour, you would only need to use 2 Tbsp. cornstarch. If you're substituting flour for cornstarch to thicken the sauce in your recipe, substitute 2 Tbsp. all-purpose flour for every 1 Tbsp. cornstarch.

Freezing cornstarch thickened mixtures is not recommended by our Test Kitchen, as the freezing process breaks down the starch thickening properties.

Making a roux of flour and butter
Credit: Andy Lyons

Other Thickening Agents

Flour and cornstarch aren't your only options to use as a food thickener. When it comes to thickening soup and other sauce-based recipes, you can make a roux (a mixture of flour and fat). This is common for creamy soups such as baked potato soup and sauces such as macaroni and cheese. (Get the full instructions on how to make roux here.) Depending on the recipe you're making, you can also use eggs, a roux, or a puree of some of the ingredients for a liquid thickener. The kind of soup thickener you use mainly depends on the recipe because some thickening agents can affect the flavor of the soup.

Put those thickening skills to good use by making chicken marsala for dinner or a delicious turkey gravy for your Thanksgiving feast. You can also make some sweet additions to your menus with a raspberry-rhubarb waffle topper or lemon curd.

Comments (1)

Better Homes & Gardens Member
September 29, 2018
My favorite thicker is making a roux with bouillon . It makes the gravy more tastier, driping from the pan . Whether it's chicken , pot roast or pork .