How to Thicken Soup: 8 Methods That Work

A soup that comes out thin and watery is easy to fix. The right way to thicken soup depends on what kind of soup it is, whether you need it gluten-free, and how much time you have. Here are eight methods, with amounts, and which soups each one suits.

Before you add anything: simmer it down

The simplest thickener is time. Simmer the soup uncovered so some of the water evaporates; the flavour concentrates as the soup thickens. This works best when the soup is only slightly thin. Taste for salt afterward, because reducing makes it saltier.

1. Cornstarch slurry

Best for clear and brothy soups, stir-fry-style sauces and when you want a quick fix.

1. For every 2 cups (480 ml) of soup, whisk 1 tablespoon cornstarch into 2 tablespoons cold water until smooth.
2. Stir the slurry into the simmering soup.
3. Simmer for 1 to 2 minutes, stirring, until the soup turns glossy and thickens. It won't reach full thickness until it bubbles.

Never add cornstarch directly to hot liquid, or it will form lumps. Cornstarch can thin out again if boiled for a long time or frozen, so add it near the end. It is naturally gluten-free.

2. Flour slurry

Whisk 2 tablespoons all-purpose flour into ¼ cup cold water or broth per 2 cups of soup, stir it in, and simmer for at least 5 minutes to cook out the raw flour taste. Flour gives an opaque, matte finish, which suits creamy and stew-like soups.

3. Roux

A roux is equal parts fat and flour cooked together, and it is the classic base for chowders and gumbo. For a medium-thick soup, cook 2 tablespoons butter with 2 tablespoons flour for 2 to 3 minutes, then gradually whisk in about 2 cups of the hot soup liquid before returning everything to the pot. A roux is easiest to add at the start of a recipe, after sautéing the vegetables.

4. Beurre manié

When a finished soup needs thickening, knead together equal amounts of soft butter and flour, about 1 tablespoon of each, into a paste. Whisk small pieces into the simmering soup until it thickens, then simmer for a few minutes. The butter coats the flour so it doesn't clump.

5. Blend part of the soup

For bean, lentil and vegetable soups, scoop out 1 to 2 cups, blend until smooth, and stir it back in. An immersion blender pulsed a few times in the pot does the same job. You get a thicker, creamier soup with no added starch or flour. If you use a countertop blender with hot soup, fill it no more than halfway and vent the lid with a towel over it.

6. Potato or bread

Starchy vegetables thicken soup naturally. Simmer a diced potato in the soup until very soft, then mash or blend it in. In a pinch, 2 to 3 tablespoons of instant potato flakes thicken about 4 cups of soup within minutes. Stale bread, torn and simmered then blended, is the traditional thickener for Italian and Spanish soups.

7. Beans, lentils or oats

A handful of red lentils simmered for 15 to 20 minutes dissolves into a soup and adds body and protein. Mashed canned white beans or a couple of tablespoons of rolled oats also work in hearty soups.

8. Cream, yogurt or cheese

Stirring in heavy cream, coconut milk, or grated Parmesan adds richness as well as some body. Add dairy at the end over low heat and don't let it boil, or it may curdle. For yogurt, temper it first by whisking in a ladle of hot soup, then stir it in off the heat.

Which thickener to choose

*Use oats labelled gluten-free if you need to avoid gluten.

If you over-thicken it

Stir in hot broth or water a little at a time until it is right, then adjust the seasoning. Soups also thicken as they cool and in the fridge, so leftover soup often needs loosening when reheated.

Our butternut squash soup and creamy tomato soup are thickened by blending alone. Cornstarch, arrowroot and other swaps are in the ingredient substitutes tool, and you can learn how to freeze soup once it's just right.