How Many Liters in a Gallon?
There are 3.78541 liters in one US gallon. This guide covers both US and imperial gallons with worked examples, a reference chart, and practical applications.
Last updated: 2025-03-15
The Short Answer
There are 3.78541 liters in one US gallon. This means a US gallon is just under four one-liter bottles. The exact value, defined by the National Institute of Standards and Technology, is 3.785411784 liters. For the imperial (UK) gallon, the answer is different: one imperial gallon equals 4.54609 liters.
The Formulas
US gallon to liters: liters = US gallons × 3.78541
Liters to US gallons: US gallons = liters / 3.78541 (or liters × 0.26417)
Imperial gallon to liters: liters = imperial gallons × 4.54609
Worked Examples
Example 1: Convert 5 US gallons to liters
- Step 1: Multiply gallons by 3.78541.
- Step 2: 5 × 3.78541 = 18.927 liters.
- Result: 5 US gallons ≈ 18.93 liters.
Example 2: Convert 10 liters to US gallons
- Step 1: Divide liters by 3.78541.
- Step 2: 10 / 3.78541 = 2.6417 gallons.
- Result: 10 liters ≈ 2.64 US gallons.
Example 3: Convert 3 imperial gallons to liters
- Step 1: Multiply by 4.54609.
- Step 2: 3 × 4.54609 = 13.638 liters.
- Result: 3 imperial gallons ≈ 13.64 liters.
Use our gallons to liters converter for instant calculations.
Quick Reference Table
| US Gallons | Liters | Imperial Gallons |
|---|---|---|
| 0.5 | 1.89 | 0.42 |
| 1 | 3.79 | 0.83 |
| 2 | 7.57 | 1.66 |
| 3 | 11.36 | 2.50 |
| 5 | 18.93 | 4.16 |
| 10 | 37.85 | 8.33 |
| 15 | 56.78 | 12.49 |
| 20 | 75.71 | 16.65 |
US Gallon vs Imperial Gallon
The US and imperial gallons diverged historically and differ by about 20%. The US gallon is defined as 231 cubic inches (3.78541 liters), while the imperial gallon is defined as the volume of 10 pounds of water at 62 °F (4.54609 liters). When reading fuel economy figures, recipe volumes, or storage capacities, always check which gallon is being referenced. US sources use the US gallon; UK, Canadian, and many Commonwealth sources may use the imperial gallon.
Real-World Applications
Fuel and Travel
Fuel in the US is sold by the gallon, while most other countries sell by the liter. If you are renting a car abroad and fuel costs 1.50 euros per liter, you can multiply by 3.785 to compare: that is about 5.68 euros per US gallon. This conversion is essential for budgeting road trips internationally.
Aquariums and Water Features
Aquarium sizes in the US are listed in gallons (e.g., a 55-gallon tank), while water treatment chemicals are often dosed per liter. A 55-gallon tank holds about 208 liters. Accurate conversion prevents over- or under-dosing water treatments.
Brewing and Beverages
Homebrew recipes may reference US gallons for batch sizes, while ingredients are measured in liters or milliliters. A standard 5-gallon batch is approximately 18.9 liters. Commercial brewing worldwide uses hectoliters (100 liters) as the standard unit.
Frequently Asked Questions
How many liters are in a US gallon?
There are exactly 3.78541 liters in one US gallon. For a quick mental estimate, remember that one US gallon is just under 3.8 liters, or roughly four liters minus about one cup.
How many liters are in an imperial gallon?
There are 4.54609 liters in one imperial (UK) gallon. The imperial gallon is about 20% larger than the US gallon.
How do I convert gallons to liters?
Multiply the number of US gallons by 3.78541. For example, 5 US gallons = 5 × 3.78541 = 18.927 liters. For imperial gallons, multiply by 4.54609 instead. Try our gallons to liters converter for instant results.