Convert US Gallon to Fluid Ounce (gal (US) → fl oz)

Converting US gallons to fluid ounces is straightforward: multiply by the conversion factor. Follow these three steps to do it by hand or in your head.

1. 1
   Take your value in US gallons

   Start with the number of US gallons (gal (US)) you want to convert.
2. 2
   Multiply by 128

   The conversion factor from gal (US) to fl oz is 128. Multiply your value by this number.
3. 3
   Read the result in fluid ounces

   The result is your value in fluid ounces (fl oz).

Multiply the value in US gallons by 128. For the reverse direction, multiply by 0.007813.

• ✓1 US gallon = 3.785 L = 128 US fluid ounces = 4 quarts.
• ✓Converting mpg (US) to L/100 km: 235.215 / mpg = L/100 km.
• ✓The US gallon is based on the old English Queen Anne wine gallon (1707).

• ✗Using UK gallons on a US fuel-economy figure — 30 mpg (US) = 36 mpg (UK).
• ✗Confusing US gallon (3.79 L) with UK gallon (4.55 L) — 20% difference.
• ✗Using "gallon" without qualifier in cross-Atlantic commerce.

What is the US Gallon?

The US liquid gallon equals exactly 3.785411784 liters and is the standard volume unit for fuel, beverages, milk, and household liquids in the United States. Defined as 231 cubic inches, the US gallon descends from the English wine gallon of 1707, which Britain replaced with the larger imperial gallon in 1824 — a divergence that left the United States with a different gallon than the rest of the English-speaking world. American gas stations price gasoline by the gallon (typical fill-up: 12–15 gallons), milk is sold in half-gallons and gallons, and many beverages come in fluid-ounce subdivisions of the gallon. The US gallon relates to the liter (1 gal ≈ 3.785 L), the quart (4 qt = 1 gal), the pint (8 pt = 1 gal), the cup (16 cups = 1 gal), and the imperial gallon (1 imp gal ≈ 1.201 US gal — about 20% larger).

• US fuel pricing and consumption
• US paint, oil and cleaning-product packaging
• US beverage containers (1-gallon jugs of milk)

What is the Fluid Ounce?

The US fluid ounce equals exactly 29.5735295625 milliliters and is the standard small-volume unit for beverages, cocktails, personal-care products, and cooking in the United States. It is distinct from the (weight) ounce: 1 fluid ounce of water weighs about 1 ounce by weight at room temperature, but other liquids may weigh more or less. Soft-drink cans (12 fl oz), beer bottles (12 fl oz), shampoo bottles, and skin-cream tubs all label volume in fluid ounces. The US fluid ounce is slightly different from the UK imperial fluid ounce (28.4131 mL — about 4% smaller), reflecting the different gallon definitions. The US fl oz relates to the gallon (128 fl oz = 1 gal), the cup (8 fl oz = 1 cup), the tablespoon (2 tbsp = 1 fl oz), and the milliliter (1 fl oz ≈ 29.57 mL). Cocktail recipes universally use fluid ounces.

• US beverage and soda can sizes (12 fl oz)
• Cosmetic and personal-care product volumes
• US fluid recipes and cocktail measures