Instantly Convert US Gallons ↔ Litres — Both Directions
Convert US gallons to litres (gal → L) or litres to US gallons (L → gal) instantly. Get the exact conversion with formula breakdown, reference table, and related unit conversions — all free, no sign-up needed.
The US gallon and the litre are both units of volume — one from the US customary system, one from the metric system. Our gallons to litres converter handles both directions instantly using the exact conversion factor: 1 US gallon = 3.785411784 litres.
The US gallon (gal) is a unit of volume used in the United States and some other countries. It is defined as exactly 3.785411784 litres. One US gallon equals 4 US quarts, 8 US pints, or 128 US fluid ounces. It is commonly used for measuring fuel, milk, water, and other liquids in the United States.
The litre (L) is a metric unit of volume equal to 1 cubic decimetre (dm³) or 1,000 cubic centimetres (cm³). It is used across most of the world for measuring liquids such as water, fuel, beverages, and cooking ingredients. One litre is equal to approximately 0.264172 US gallons or 1,000 millilitres.
The exact conversion factor is 1 US gallon = 3.785411784 litres, as defined by the US National Institute of Standards and Technology (NIST). For the reverse, 1 litre = 0.264172052 US gallons. Note that the US gallon differs from the UK (Imperial) gallon — 1 UK gallon = 4.54609 litres — so always confirm which gallon is being used.
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The conversion between US gallons and litres uses an exact, internationally defined factor. One US gallon is defined as exactly 3.785411784 litres — this is not an approximation. Both formulas below are mathematically exact and are the same values used by NIST and international standards bodies in 2026.
The table below lists commonly needed US gallon-to-litre conversions. All values use the exact factor of 1 US gal = 3.785411784 L. Additional columns show millilitres and US quarts for quick cross-reference with related volume units.
| US Gallons (gal) | Litres (L) | Millilitres (mL) | US Quarts (qt) | Common Context |
|---|---|---|---|---|
| 0.25 gal | 0.9464 L | 946.4 mL | 1 qt | 1 US quart |
| 0.5 gal | 1.8927 L | 1892.7 mL | 2 qt | Half gallon jug |
| 1 gal | 3.7854 L | 3785.4 mL | 4 qt | Standard milk jug (US) |
| 2 gal | 7.5708 L | 7570.8 mL | 8 qt | Large water jug |
| 3 gal | 11.3562 L | 11356.2 mL | 12 qt | Fish tank (small) |
| 5 gal | 18.9271 L | 18927.1 mL | 20 qt | Standard US water cooler jug |
| 10 gal | 37.8541 L | 37854.1 mL | 40 qt | Small aquarium |
| 15 gal | 56.7812 L | 56781.2 mL | 60 qt | Medium aquarium |
| 20 gal | 75.7082 L | 75708.2 mL | 80 qt | Large aquarium / fuel tank fill |
| 25 gal | 94.6353 L | 94635.3 mL | 100 qt | Compact car fuel tank |
| 30 gal | 113.562 L | 113562 mL | 120 qt | Residential water heater |
| 50 gal | 189.271 L | 189271 mL | 200 qt | Large residential water heater |
| 100 gal | 378.541 L | 378541 mL | 400 qt | Commercial water storage |
| 500 gal | 1892.71 L | 1892706 mL | 2000 qt | Rainwater collection tank |
Need to convert the other way? The table below shows common litre values converted to US gallons. All values use the exact factor of 1 L = 0.264172052 US gallons.
| Litres (L) | US Gallons (gal) | US Quarts (qt) | Millilitres (mL) |
|---|---|---|---|
| 1 L | 0.2642 gal | 1.0567 qt | 1000 mL |
| 2 L | 0.5284 gal | 2.1134 qt | 2000 mL |
| 3 L | 0.7925 gal | 3.1701 qt | 3000 mL |
| 4 L | 1.0567 gal | 4.2268 qt | 4000 mL |
| 5 L | 1.3209 gal | 5.2834 qt | 5000 mL |
| 10 L | 2.6417 gal | 10.5669 qt | 10000 mL |
| 20 L | 5.2834 gal | 21.1338 qt | 20000 mL |
| 25 L | 6.6043 gal | 26.4172 qt | 25000 mL |
| 40 L | 10.5669 gal | 42.2675 qt | 40000 mL |
| 50 L | 13.2086 gal | 52.8344 qt | 50000 mL |
| 100 L | 26.4172 gal | 105.669 qt | 100000 mL |
| 200 L | 52.8344 gal | 211.338 qt | 200000 mL |
| 1000 L (1 m³) | 264.172 gal | 1056.69 qt | 1000000 mL |
The US gallons-to-litres conversion is one of the most common volume conversions worldwide — needed any time you interact with US-based fuel, food, or fluid measurements in a metric context. Here are the most frequent real-world scenarios.
In the US, fuel is sold by the gallon, while the rest of the world uses litres. A car with a 15-gallon tank = 56.78 litres. Travellers renting a car in the US, or Americans driving abroad, regularly need this conversion to understand fuel costs and tank capacity. In 2026, the average US car fuel tank holds 12–16 gallons = 45–60 litres.
Milk, juice, and other beverages are sold in gallons and half-gallons in US supermarkets, while the same products are sold in litres everywhere else. A 1-gallon milk jug = 3.785 litres. Recipes from US cookbooks often list liquid measurements in cups and gallons that need converting for metric cooks. 1 US cup = 0.0625 gallons = 236.6 mL.
Aquarium sizes in the US are labelled in gallons — a "10-gallon tank" = 37.85 litres, a "55-gallon tank" = 208.2 litres. Fish keepers worldwide need this conversion when buying filtration equipment, calculating water treatments, and following care guides that use different measurement systems. This is one of the most searched gallon conversions online.
US pool volumes are quoted in gallons — a standard backyard pool holds 10,000–20,000 gallons = 37,854–75,708 litres. Pool chemical dosing instructions often list quantities per 10,000 gallons or per 1,000 litres, so converting between the two is essential for accurate water treatment, especially when using products from different countries.
Irrigation systems, fertiliser mixing ratios, and pesticide dilutions in the US are expressed in gallons per acre or gallons per hour. Converting these to litres helps international farmers and gardeners follow US agricultural guidelines. A garden sprayer rated at 2 gallons = 7.57 litres of capacity.
US fuel economy is measured in miles per gallon (MPG), while most countries use litres per 100 kilometres (L/100km). Converting between these systems requires understanding the gallon-to-litre relationship. A car getting 30 MPG US uses approximately 7.84 L/100km — an essential conversion for anyone comparing international vehicle specs or calculating fuel costs abroad. Learn more at fueleconomy.gov.
The National Institute of Standards and Technology (NIST) publishes the official definition of the US gallon, its exact metric equivalent (3.785411784 litres), and all other US customary volume units. NIST is the authoritative source for US measurement standards in 2026.
Visit NIST →The US Department of Energy's fueleconomy.gov site provides official fuel economy ratings in MPG for all US vehicles. Understanding MPG requires knowing how gallons relate to litres — essential for comparing US and international vehicle efficiency figures.
Visit fueleconomy.gov →ConcreteMetric.com offers a growing library of free, accurate unit converters for volume, length, area, energy, time, pressure, and more — all fully mobile-friendly and updated for 2026.
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