US Gallon (US gal)
Definition
The US gallon (symbol US gal) is a unit of volume in the US customary system equal to exactly 3.785411784 liters or 231 cubic inches. It contains 4 US quarts, 8 US pints, 16 US cups, or 128 US fluid ounces.
History
The US gallon descends from the English wine gallon of 1707, which was defined as 231 cubic inches. The United States retained that definition when Britain adopted a new imperial gallon of 4.54609 liters in 1824, leading to the modern split between the two systems.
The US gallon is the primary fuel-volume unit in the United States, used on gasoline pumps, EPA fuel-economy ratings (MPG), and most domestic liquid retail. NIST aligned it with metric units in 1893 via the Mendenhall Order; the modern value is exactly 3.785411784 L.
Standard reference
Defined under the Mendenhall Order (1893) and confirmed by NIST Handbook 44 as exactly 231 in³ = 3.785411784 L. Used by EPA fuel-economy ratings.
Common conversions
| 1 US gal | = 3.785411784 L |
|---|---|
| = 3,785.41 mL | |
| = 128 US fl oz | |
| = 16 US cups |