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Roux Thickening Calculator

Size a butter-and-flour roux for a soup, sauce or gravy, or work backwards from a roux you already have to the liquid it will thicken.

the quantity you already know
2 level tbsp of flour per cup of liquid
stock, milk or the liquid in the pan
0.25–25 cups, 60–6000 mL, 0.06–6 L
Enter a liquid volume to see the flour and butter it needs.

Uses the classic home roux rule of one, two or three level tablespoons of flour per US cup of liquid for a thin soup, a medium sauce and a thick gravy. A US cup is 236.588 mL and a level tablespoon of all-purpose flour is 8 g, so the three settings work out to about 3.4%, 6.8% and 10.1% flour by weight in a water-like liquid. Butter is measured to match the flour's volume (1 tbsp = 14.2 g), the usual kitchen ratio, which is about 1.8 times the flour's weight. A roux carries no salt, so season the sauce separately, and flour keeps thickening as it simmers and cools — add liquid rather than more flour if it overshoots. The page does not cover cornstarch slurries, reductions or other thickeners, and it is a cooking estimate rather than food-safety guidance. Everything runs in your browser with no storage, uploads or network access.