The US gallon (abbreviated as "gal") and the liter (abbreviated as "L") are two of the most widely used units of volume and liquid capacity in the world. While the US gallon is primarily utilized in the United States and a few other countries adhering to the US customary system, the liter is the standard metric unit of volume used globally in scientific, industrial, and everyday applications.
The US liquid gallon is historically defined based on the wine gallon, which was standardized as 231 cubic inches. In contrast, the liter is defined within the International System of Units (SI) as being equal to one cubic decimeter (\\(1 \\text{ dm}^3\\)).
The Conversion Factor
To convert US gallons to liters, we use the exact conversion factor defined by international standards:
This precise factor is critical in chemical processing, fluid dynamics, and international trade where exact liquid measurements are required. For most everyday estimations, rounding the factor to \\(3.7854\\) or even \\(3.8\\) is sufficient.
Practical Applications
Automotive Industry: Fuel economy ratings (miles per gallon vs. liters per 100 kilometers) and fuel tank capacities.
Chemical & Process Engineering: Scaling batch recipes from laboratory scale (liters) to pilot or production scale (gallons).
Consumer Goods: Packaging sizes for beverages, paints, and industrial lubricants exported between metric and imperial-using nations.
Gallon (US) to Liter Conversion Reference Table
Gallon (US) (gal)
Liter (L)
0.1
0.3785
0.5
1.8927
1.0
3.7854
2.0
7.5708
5.0
18.9271
10.0
37.8541
20.0
75.7082
50.0
189.2706
100.0
378.5412
500.0
1892.7059
1000.0
3785.4118
Step-by-Step Conversion Example
To convert a volume from US gallons to liters, multiply the volume in gallons by the conversion factor \\(3.785411784\\).
For practical engineering purposes, this can be rounded to four decimal places: 37.8541 L.
No, they are different. The US liquid gallon is approximately \\(3.785\\) liters, whereas the Imperial gallon (used historically in the UK and still used in some Commonwealth nations) is larger, defined as exactly \\(4.54609\\) liters. Always ensure you verify which gallon is being referenced in engineering specifications.
For a quick mental approximation, you can multiply the gallon value by \\(4\\) and then subtract \\(5\\%\\) from the result. For example, for 10 gallons: \\(10 \\times 4 = 40\\), and subtracting \\(5\\%\\) (which is \\(2\\)) gives \\(38\\) liters, which is very close to the actual value of \\(37.85\\) liters.
"On fait la science avec des faits, comme on fait une maison avec des pierres ; mais une accumulation de faits n'est pas plus une science qu'un tas de pierres n'est une maison." "Science is built up of facts, as a house is built of stones; but an accumulation of facts is no more a science than a heap of stones is a house." — Henri Poincaré (French Mathematician, Theoretical Physicist & Mining Engineer)