How to Use Flour or Cornstarch to Thicken Sauce, Gravy, and Soup (2024)

Learn how to thicken a sauce with just two simple ingredients: flour or cornstarch. Plus, get a gluten-free thickener option, too.

Katlyn Moncada

Katlyn Moncada is the associate food editor at BHG.com, sharing food news and tutorials on becoming better home cooks. She is a writer and editor with nearly a decade of experience in digital media, photography, and video production.

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Updated on August 28, 2023

Fact checked by

Marcus Reeves

Fact checked byMarcus Reeves

Marcus Reeves is an experienced writer, publisher, and fact-checker. He began his writing career reporting for The Source magazine. His writing has appeared in The New York Times, Playboy, The Washington Post, and Rolling Stone, among other publications. His book Somebody Scream: Rap Music's Rise to Prominence in the Aftershock of Black Power was nominated for a Zora Neale Hurston Award. He is an adjunct instructor at New York University, where he teaches writing and communications. Marcus received a Bachelor of Arts degree from Rutgers University in New Brunswick, New Jersey.

How to Use Flour to Thicken Sauce

To use flour as a thickening agent:

Use two tablespoons flour mixed with ¼ cup cold water for each cup of medium-thick sauce.
Thoroughly mix in the water 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 cook the flour thoroughly.

How to Use Cornstarch to Thicken Sauce

Using cornstarch to thicken sauce is very similar to using flour, but you need different quantities:

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

Test Kitchen Tip

Be careful not to overcook cornstarch-thickened sauces. 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

If you have someone in the family with an allergy restriction, you may need a gluten-free thickener for your soup recipe. It's important to note that cornstarch has twice the thickening power of flour. If you need to substitute cornstarch to thicken liquid in a recipe that calls for ¼ cup (four tablespoons) flour, you only need two tablespoons cornstarch. If you're substituting flour for cornstarch to thicken the sauce in your recipe, substitute two tablespoons all-purpose flour for every one tablespoon cornstarch.

Test Kitchen Tip

We don't recommend freezing cornstarch-thickened mixtures, as the freezing process breaks down the starch-thickening properties.

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How to Use Flour or Cornstarch to Thicken Sauce, Gravy, and Soup (4)

Other Thickening Agents

There are options other than flour and cornstarch to thicken foods. 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 like baked potato soup and sauces like macaroni and cheese. (Get the full instructions on how to make roux here.)

Depending on your recipe, you can use eggs, a roux, or a puree of ingredients for a liquid thickener. The soup thickener depends on the recipe because some thickening agents can affect the soup's flavor.

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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.

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As a seasoned culinary expert with extensive experience in recipes and cooking techniques, let me delve into the intricacies of thickening sauces, a fundamental skill in the culinary world. The article you provided, authored by Katlyn Moncada, the associate food editor at BHG.com, is a valuable resource for home cooks seeking to enhance the texture and flavor of their dishes.

Firstly, let's acknowledge the credibility of the information through the fact-checking process conducted by Marcus Reeves, an experienced writer, publisher, and fact-checker. With a background that includes contributions to reputable publications like The New York Times, Playboy, and Rolling Stone, Reeves brings a wealth of expertise to ensure the accuracy of the content.

Now, let's explore the key concepts covered in the article:

1. How to Use Flour to Thicken Sauce:

Combine two tablespoons of flour with ¼ cup of cold water for each cup of medium-thick sauce.
Ensure thorough mixing to prevent lumps.
Stir the flour-water mixture into the sauce and cook over medium heat until thickened and bubbly.
Allow an additional minute of cooking to ensure the flour is thoroughly cooked.

2. How to Use Cornstarch to Thicken Sauce:

Mix one tablespoon of cornstarch with one tablespoon of cold water (cornstarch slurry) for each cup of medium-thick sauce.
Thoroughly combine the cornstarch slurry and pour it into the sauce.
Cook and stir over medium heat until thickened and bubbly.
Extend the cooking time to two more minutes to completely cook the cornstarch.

3. Substituting Cornstarch for Flour as a Gluten-Free Alternative:

Cornstarch is suggested as a gluten-free thickener.
Note that cornstarch has twice the thickening power of flour.
The substitution ratio is two tablespoons of cornstarch for every one tablespoon of flour in a recipe.

4. Other Thickening Agents:

Roux, a mixture of flour and fat, is introduced as an alternative thickening method, especially for creamy soups and sauces like macaroni and cheese.
Depending on the recipe, eggs, roux, or a puree of ingredients can be used as liquid thickeners.
Emphasizes the importance of choosing thickening agents based on the recipe, considering the potential impact on flavor.

5. Additional Tips:

Caution against overcooking cornstarch-thickened sauces, as overcooking can lead to a breakdown of thickening properties.
Not recommended to freeze cornstarch-thickened mixtures due to the freezing process affecting the starch-thickening properties.

In conclusion, this comprehensive guide equips readers with the knowledge and techniques needed to master the art of thickening sauces. Whether you're preparing savory dishes like chicken marsala or delightful treats like raspberry-rhubarb waffle topper, the article provides valuable insights to elevate your culinary skills.