All-purpose flour vs Cornstarch
As thickeners they behave differently. Cornstarch has about twice the thickening power of flour, so 1 tablespoon of cornstarch thickens as much as 2 tablespoons of flour. Cornstarch sets clear and glossy, which suits fruit pies and stir-fry sauces; flour sets cloudy, which is fine for gravies and roux. Flour can simmer for a long time, but cornstarch thins out if you overcook or over-stir it, so add it near the end.
At a glance
| Ingredient | Grams per cup | Type | Key trait |
|---|---|---|---|
| All-purpose flour | 120 g | Flours & Starches | Spoon the flour into the cup and level it off — scooping straight from the bag packs it down and can add up to 20% more flour than a recipe intends. |
| Cornstarch | 120 g | Flours & Starches | Cornstarch is fine and powdery — stir it before measuring to break up any lumps. |
How to swap all-purpose flour and cornstarch
- 1 cup AP = ⅞ cup cake flour + 2 tbsp cornstarch (for cake-flour recipes) (America's Test Kitchen)Use when a recipe calls for cake flour and you only have AP; for the reverse, equal parts bread + cake flour by weight approximates AP.
- 1 tbsp cornstarch = 2 tbsp all-purpose flour (for thickening sauces) (America's Test Kitchen)Make a slurry with 2 parts cold water, 1 part flour; whisk smooth before adding to the simmering liquid. Simmer 2–3 minutes longer than usual to cook out the raw flour taste.
Full conversions: All-purpose flour converter · Cornstarch converter. More swaps: All-purpose flour substitutes · Cornstarch substitutes.
More comparisons
* Conversion figures are typical average weights for one US customary cup (236.6 ml), based on the King Arthur Baking Ingredient Weight Chart and cross-referenced with the U.S. Department of Agriculture FoodData Central database. Actual weight varies with packing, brand and humidity — see our methodology.