gal (US) US customary / imperial
Measures: Volume — how much space
US gallon
The US fuel-and-milk unit.
VolumeHow it's defined
Defined as exactly 231 cubic inches, which works out to exactly 3.785411784 litres. Not the same as the imperial gallon — a 20% trap between neighbors.
1 US gal = 3.785411784 L — exact1 imperial gal = 4.54609 L — exact, and bigger
Convert — honestly
gal (US) equals
3.78541178 L
Litre · factor exact — the base unit for this page
0.832674185 gal (imp)
Imperial gallon · factor exact — exact by definition (UK, 1985)
Conversions run through the litre using the stated factors — no rounding beyond display precision, and every factor says whether it's exact or measured.
Where you meet it
- US gas stations and milk jugs
- The "miles per gallon" number depends on which gallon
Other ways to measure volume
Source
This page is an authored summary of the authoritative definition — checkable one click away.
NIST Special Publication 811 — Guide for the Use of the SI