What is the right ratio of fat to flour for a roux?

Classic roux is 1:1 fat-to-flour by WEIGHT (not volume). 1 oz butter + 1 oz flour = 2 oz roux thickens ~1 quart liquid. Type determines color: white (2 min), blonde (5 min), brown (10 min), dark/cajun (30+ min).

The full answer

Roux is the French culinary base — equal parts fat and flour cooked together, then used to thicken sauces, gravies, and soups. The ratio is precise but the cook time + temperature determine the color + flavor.

**Standard ratio: 1:1 by weight** - 28g butter + 28g flour = 56g roux - 1 oz butter + 1 oz flour = 2 oz roux - 2 tbsp butter + 2 tbsp flour = 4 tbsp roux (close enough to 1:1 by weight)

**Why weight, not volume:** - 2 tbsp butter weighs 28g; 2 tbsp flour weighs 16g - Volume ratio works approximately because butter melts and disperses - Weight ratio is precise: 1:1 always

**Roux types by color + cook time:**

**White roux (béchamel, white sauces):** - Cook time: 1–2 minutes (very brief; just removes raw flour taste) - Color: pale yellow - Use: béchamel, mac and cheese, alfredo, white pizza sauce - Thickening power: highest (least Maillard, most pure starch)

**Blonde roux (light gravies, velouté):** - Cook time: 3–5 minutes - Color: light golden - Use: velouté, light gravies, sauce normande - Thickening power: slightly less than white (slight Maillard breakdown)

**Brown roux (red sauces, gravy):** - Cook time: 10–15 minutes - Color: peanut-butter brown - Use: brown gravy, espagnole, beef stew, mushroom sauces - Thickening power: reduced by ~25% - Flavor: nutty, complex

**Dark/Cajun roux (gumbo):** - Cook time: 30–45 minutes (some chefs 60+ minutes) - Color: chocolate-brown to mahogany - Use: Cajun gumbo (Louisiana classic) - Thickening power: very low (~50% of white roux) - Flavor: deep nutty, almost like chocolate - "The roux is the soul of gumbo"

**Method:** 1. Melt fat (butter, oil, or animal fat) in heavy-bottomed pan at medium heat 2. Add flour all at once 3. Whisk constantly to combine 4. Continue whisking as it cooks to target color 5. Add liquid gradually while whisking to prevent lumps

**Thickening capacity:** - 1 oz (28g) roux thickens ~1 quart (32 oz) of liquid to medium sauce consistency - 1.5 oz roux for thick gravy - 0.5 oz roux for thin sauce - Cajun-dark roux: use 1.5-2× more for same thickening

**Fat type variations:** - **Butter (classic French)**: rich, milky, browns quickly. Standard for béchamel + white sauces. - **Vegetable oil**: more neutral, withstands higher temps; used for dark roux + Cajun (canola, peanut, sunflower) - **Animal fat (bacon grease, schmaltz, duck fat)**: deeper flavor, traditional for some applications - **Ghee/clarified butter**: highest smoke point, premium choice for medium-dark roux

**The "cold roux + hot liquid" or "hot roux + cold liquid" rule:** - One must be cold, the other hot, for smooth thickening - Both same temp = lumps + uneven thickening - Standard: roux cools 30 sec while whisking liquid into it; OR roux + cold milk whisked together off heat

**Don't:** - Skip the cook (raw flour taste in finished sauce) - Stop whisking dark roux (burns in seconds — burned roux = bitter unusable) - Cook over high heat (uneven; burns flour before fat properly absorbs) - Add wet liquid all at once (lumps); whisk in slowly

**Variations + alternatives:** - **Beurre manié**: equal-parts cold butter + flour kneaded together; whisked into hot liquid; no cooking. Same thickening, no roux flavor. - **Cornstarch slurry**: 1 tbsp cornstarch + 2 tbsp cold water; whisked into hot liquid; thickens immediately. Glossier, lighter than roux. - **Arrowroot slurry**: similar to cornstarch but freezes/reheats better - **Reduction**: just simmer liquid until thickened (no thickener); time-consuming but flavor-intense

**Cross-reference:** see /pages/how-long-does/caramelizing-onions for similar Maillard-reaction methodology + /pages/how-long-does/pizza-dough-rise for related ratio-based cooking.

Most published references (Julia Child "Mastering the Art", Auguste Escoffier "Le Guide Culinaire", Joy of Cooking, Paul Prudhomme "Chef Paul Prudhomme's Louisiana Kitchen") converge on 1:1 by weight as the classical standard.

Time ranges by condition

What changes the time

• Fat type. Butter for white/blonde; oil for brown/dark (withstands long cook better)
• Cook time. Determines color + flavor; longer = darker + nuttier + less thickening power
• Flour type. All-purpose standard; bread flour adds slightly more thickening; whole wheat works but produces grittier sauce
• Temperature. Medium heat ideal; high = burn; low = won't darken

Common questions

Sources

We cite primary research, expert practice, and authoritative reference. Higher-tier sources weighted heavier. See methodology.

1. T2Julia Child + Simone Beck, "Mastering the Art of French Cooking, Vol. 1" — Canonical English reference for classical French roux methodology
2. T2Auguste Escoffier, "Le Guide Culinaire" (1903) — Foundational French culinary reference; defines roux for modern cuisine
3. T2The Joy of Cooking — Standard home reference for roux + variations + thickening calculations
4. T2Paul Prudhomme, "Chef Paul Prudhomme's Louisiana Kitchen" — Definitive Cajun cooking + dark roux methodology

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