Convert US Gallons to Liters
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Measurement
About US Gallons to Liters Conversions
One Gallon = 3.785 Liters (Exactly)
The US gallon is defined as exactly 231 cubic inches, which works out to 3.785411784 liters. This is one of the cleaner conversions in the imperial-metric world, because both are based on exact definitions. For everyday use, 3.785 is precise enough. For rough mental math, use 3.8.
Fuel Economy Comparison
When an American car review says "a 15-gallon fuel tank," that is 56.8 liters. European reviews of the same car will list the tank as 57 liters (rounded). This conversion matters when comparing car specs across markets.
| US Gallons | Liters | Context |
|---|---|---|
| 1 | 3.785 | The base conversion |
| 2 | 7.571 | Small gas can |
| 5 | 18.93 | Homebrew batch / jerry can |
| 10 | 37.85 | Compact car fuel tank |
| 15 | 56.78 | Average sedan fuel tank |
| 20 | 75.71 | SUV fuel tank |
| 40 | 151.4 | Large truck fuel tank |
| 55 | 208.2 | Standard US drum |
| 100 | 378.5 | Small water tank |
Aquariums: Gallons Define the Hobby in the US
American aquarium sizes are always stated in gallons. A "20-gallon long" is 75.7 liters. A "55-gallon" tank is 208 liters. Fish medication dosing instructions from European manufacturers specify amounts per liter, while your tank is labeled in gallons. Overdosing or underdosing aquarium chemicals because of a conversion error can kill fish. The 3.785 factor is worth knowing precisely in this context.
Standard aquarium sizes: 10 gal (37.9 L), 20 gal (75.7 L), 29 gal (109.8 L), 55 gal (208.2 L), 75 gal (283.9 L), 125 gal (473.2 L).
Water Usage and Conservation
Home water usage in the US is measured in gallons. The average American uses about 80 gallons (303 liters) of water per day. A standard bathtub holds 40-50 gallons (151-189 liters). A standard washing machine uses 15-30 gallons (57-114 liters) per load. Water utilities in the US bill per 1,000 gallons (3,785 liters, or roughly 3.8 cubic meters).
When comparing water costs internationally, the liter conversion puts everyone on the same scale. US water at $3 per 1,000 gallons is about $0.79 per cubic meter, which is inexpensive by European standards.
Why Two Gallons Exist
The US gallon (3.785 L) and the imperial gallon (4.546 L) diverged in 1824 when the UK redefined its gallon based on the weight of water. The US kept the older Queen Anne wine gallon, defined by statute in 1706. This 20% difference means that fuel economy figures, recipes, and tank sizes from UK sources will not match US gallon-based numbers. Always check which gallon is being used.
Quick Conversions
| Unit Name | Symbol | Per 1 US Gallon |
|---|---|---|
| Cubic Centimeter | cm³ | 3785.41 |
| Cubic Foot | ft³ | 0.133681 |
| Cubic Inch | in³ | 231 |
| Cubic Meter | m³ | 0.00378541 |
| Imperial Fluid Ounce | imp fl oz | 133.228 |
| Imperial Gallon | imp gal | 0.832674 |
| Imperial Pint | imp pt | 6.66139 |
| Liter | L | 3.78541 |
| Milliliter | mL | 3785.41 |
| US Cup | US cup | 16 |
| US Fluid Ounce | US fl oz | 128 |
| US Gallon | US gal | 1 |
| US Pint | US pt | 8 |
| US Quart | US qt | 4 |
| US Tablespoon | US tbsp | 256 |
| US Teaspoon | US tsp | 768 |
Frequently Asked Questions
How do I convert US Gallons to Liters?
To convert US Gallons to Liters, use the conversion where 1 US Gallon (US gal) = 3.78541 Liters (L). For example, 1 US Gallon = 3.78541 Liters.
What are common US Gallon to Liter conversions?
Here are common conversions: 1 US Gallons = 3.78541 Liters, 5 US Gallons = 18.9271 Liters, 10 US Gallons = 37.8541 Liters, 25 US Gallons = 94.6353 Liters, 50 US Gallons = 189.271 Liters, 100 US Gallons = 378.541 Liters.
When would I need to convert US Gallons to Liters?
Converting US vehicle fuel tank specs for international markets. Purchasing aquarium or pool supplies in metric-sized containers. Scaling US recipes for metric measuring equipment.
How precise are the conversions?
All conversions use exact factors verified against NIST and ISO standards with up to 10 significant figures of precision. Results are calculated using IEEE 754 double-precision arithmetic, which provides approximately 15-17 significant digits. For temperature and other non-linear conversions, exact formulas are used rather than approximations.
How many Liters is 1 US Gallons? (One US gallon — a common milk jug size)
1 US Gallons equals 3.785 L Liters. This is a frequently referenced value because it represents one us gallon — a common milk jug size.