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US Gallons to Liters

1 US Gallon (gal) = 3.78541 Liter (L)

Result
3.78541 L
1 gal = 3.78541 L

How Many Liters in a Gallon?

To convert US gallons to liters, multiply the number of gallons by 3.78541. One US gallon equals 3.78541 liters, or roughly 3.8 liters for quick estimates. This conversion is essential when adapting American recipes that call for gallon quantities to metric measurements, understanding US fuel tank capacities in metric terms, calculating liquid volumes for international shipping, or converting pool and spa volumes. Because the gallon is a uniquely American unit in modern usage (with the exception of a few countries that use the slightly different Imperial gallon), anyone moving between US and metric measurement systems needs this conversion regularly.

How to Convert US Gallon to Liter

  1. Start with the volume in US gallons that you want to convert.
  2. Multiply the gallon value by 3.78541 to get the equivalent volume in liters.
  3. For a quick mental estimate, multiply by 4 and subtract about 5%. For instance, 5 gallons × 4 = 20, minus 5% (1 liter) = roughly 19 liters (exact: 18.93 liters).
  4. If converting from Imperial gallons instead, multiply by 4.54609.
  5. Verify your result makes sense: the liter value should always be roughly 3.8 times the gallon value.

Real-World Examples

Converting a US recipe — A recipe calls for 1/2 gallon of chicken stock
0.5 × 3.78541 = 1.893 liters. Round to 1.9 liters, or use 2 liters for simplicity — the slight excess will not affect most recipes.
Fuel tank capacity — A truck with a 36-gallon tank
36 × 3.78541 = 136.27 liters. For context, many European cars have tanks in the 50- to 70-liter range, so a 136-liter tank is quite large by international standards.
Water heater capacity — A 40-gallon water heater
40 × 3.78541 = 151.42 liters. Water heaters sold internationally are typically rated in liters, so a US 40-gallon model is equivalent to a 150-liter unit.
Paint coverage — 1 gallon of paint covers 400 sq ft
1 gallon = 3.785 liters. If paint is sold in 4-liter cans internationally, one 4-liter can is slightly more than 1 US gallon and will provide comparable coverage.

Quick Reference

US Gallon (gal) Liter (L)
1 3.78541
2 7.57082
5 18.9271
10 37.8541
25 94.6353
50 189.271
100 378.541
500 1892.71
1,000 3785.41

History of US Gallon and Liter

The word "gallon" derives from the Old French "galon" or "jalon," a measure for liquids. Throughout English history, multiple gallons coexisted — the wine gallon, the ale gallon, and the corn gallon all had different volumes. When the United States became independent, it standardized on the Queen Anne wine gallon of 231 cubic inches (3.78541 liters), which had been defined by an act of the British Parliament in 1706. Britain consolidated its various gallons into the single Imperial gallon in 1824, defining it as the volume of 10 pounds of distilled water at 62°F. This produced a gallon of approximately 277.42 cubic inches, or 4.54609 liters — significantly larger than the US gallon. The divergence means that a "gallon" in the US and a "gallon" in the UK or countries that inherited the Imperial system (like some Caribbean nations) refer to different volumes, a source of ongoing confusion. The liter, by contrast, has a single universal definition. Originally tied to a cubic decimeter, it was briefly redefined in 1901 as the volume of 1 kilogram of water at maximum density, then reverted to the cubic decimeter definition in 1964. Today, 1 liter = 1 cubic decimeter = 0.001 cubic meters, providing a clean and unambiguous standard.

Common Mistakes to Avoid

  • Using the Imperial gallon conversion factor (4.546) when the source uses US gallons (3.785). Always identify which gallon system is being used before converting.
  • Assuming "a gallon is about 4 liters" and leaving it at that. The difference between 3.785 and 4.0 is about 5.7%, which is significant for precise applications like fuel tracking or chemical mixing.
  • Neglecting to distinguish between US liquid gallons and the rarely used US dry gallon (4.405 liters). Almost all everyday references to "gallons" in the US mean liquid gallons.
  • Reversing the multiplication — dividing by 3.785 instead of multiplying. Dividing converts liters to gallons, not gallons to liters.

Frequently Asked Questions

How many liters is 1 gallon of water?
One US gallon of water equals 3.785 liters. By weight, this is approximately 3.785 kilograms (since water has a density of about 1 kg per liter at room temperature), or about 8.34 pounds.
How many liters in 5 gallons?
5 US gallons equals 18.927 liters. A standard 5-gallon bucket used in the US is roughly equivalent to a 19-liter bucket in metric countries.
Is a gallon the same everywhere?
No. The US gallon (3.785 liters) and the Imperial gallon (4.546 liters) are different sizes. A few countries like Liberia and Myanmar also use the US gallon. Some Caribbean and former British colonies may still reference Imperial gallons. Always specify which gallon you mean.
How do I convert gallons per mile to liters per 100 km?
Multiply the gallons-per-mile figure by 378.541 to get liters per 100 km. Alternatively, divide 235.215 by the MPG value. For example, 30 MPG = 235.215 / 30 = 7.84 L/100 km.
Why is the US gallon smaller than the Imperial gallon?
The US adopted the English wine gallon (231 cubic inches) before Britain reformed its measurement system in 1824. When Britain created the Imperial gallon (277.42 cubic inches) based on the weight of water, the US kept its original standard. The two countries simply chose different reference points.
Quick Tip

A handy set of gallon-to-liter benchmarks: 1 gallon is about 3.8 liters, 5 gallons is about 19 liters, 10 gallons is about 38 liters, and 100 gallons is about 379 liters. For fuel economy conversions, remember the magic number 235.215: divide it by MPG to get liters per 100 km, or divide it by L/100km to get MPG. This works for US gallons; for Imperial MPG, use 282.481 instead.