Capacity Converter - Liters to US & UK Gallons

Three liquid volume units, one tool

A US fuel pump reads 13.2 gallons. Your rental car manual says the tank holds 50 liters. A British recipe calls for half an Imperial gallon of stock. These are three different units for the same thing - liquid volume - and mixing them up is surprisingly easy. This converter handles all three: liters (L), US gallons and UK (Imperial) gallons. The critical difference? A US gallon is 3.785 liters. A UK gallon is 4.546 liters. That 20% gap has confused travelers, importers and cooks for centuries.

How to convert capacity - step by step

Enter the value - type the volume you want to convert. Decimals are fine (e.g. 15.5).
Select the source unit - liters, US gallons or UK (Imperial) gallons. If you are unsure which gallon type, the US gallon is used in North America, the UK gallon in Britain and some Commonwealth countries.
Select the target unit - pick the unit you need the result in.
Read the result - the converter shows the converted value, the formula used and a step-by-step breakdown.

Quick start: Converting a 50 L tank to US gallons? Enter 50, select Liters as source, US Gallons as target. Result: 13.21 US gal.

Conversion reference table

The table below shows common volume conversions between liters, US gallons and UK gallons. All values rounded to 2 decimal places.

Liters (L)	US Gallons	UK Gallons	Typical use
1	0.26	0.22	Water bottle
3.785	1.00	0.83	1 US gallon (milk jug)
4.546	1.20	1.00	1 UK gallon (Imperial)
10	2.64	2.20	Jerry can
20	5.28	4.40	Motorcycle tank
45	11.89	9.90	Small car tank (VW Polo)
60	15.85	13.20	Mid-size sedan tank
80	21.13	17.60	Large SUV / pickup tank
100	26.42	22.00	Truck / auxiliary tank

US gallon vs UK gallon - why the difference matters

Property	US Gallon	UK (Imperial) Gallon
Volume in liters	3.78541 L	4.54609 L
Volume in fluid ounces	128 fl oz (US)	160 fl oz (UK)
Used in	USA, Liberia, Myanmar	UK (fuel economy only)
MPG comparison	30 MPG (US) = 7.84 L/100km	30 MPG (UK) = 9.42 L/100km
Ratio	1 UK gallon = 1.201 US gallons (20.1% larger)

Practical scenarios

Scenario 1 - Refueling in the US: You filled up 15 US gallons at a gas station in Florida. How many liters?
Result: 15 x 3.785 = 56.78 L - about a full tank for a mid-size rental car.

Scenario 2 - UK fuel economy: A British car review says 45 MPG (Imperial). What does that mean in liters?
Result: 1 UK gal = 4.546 L, so 45 MPG (UK) = 6.28 L/100km. The same car in the US would be rated 37.5 MPG (US).

Scenario 3 - Car import: A Mustang for sale in Texas lists a 16-gallon tank. How many liters?
Result: 16 x 3.785 = 60.57 L - a standard tank for a V8 coupe.

Scenario 4 - Cooking (large batch): An old British recipe calls for 2 Imperial gallons of water for brining a turkey.
Result: 2 x 4.546 = 9.09 L - about nine one-liter bottles.

Scenario 5 - Motorcycle: A Harley-Davidson lists a 4.7 US gallon fuel tank. Liters?
Result: 4.7 x 3.785 = 17.79 L - typical for a touring motorcycle.

Scenario 6 - Pool chemicals: You need 1 gallon of chlorine per 10,000 gallons of pool water. Your pool is 45,000 L. How many gallons of chlorine?
Pool = 45,000 / 3.785 = 11,889 US gal. You need about 1.19 gallons of chlorine.

FAQ - Frequently asked questions

How many liters are in 1 US gallon?

Exactly 3.78541 liters. For quick mental math, multiply gallons by 3.8 - close enough for refueling estimates. So 10 US gallons is roughly 38 liters, and 15 US gallons is roughly 57 liters.

Why is the UK gallon bigger than the US gallon?

Historical divergence. The Imperial gallon was defined in 1824 as the volume of 10 pounds of water at 62 F - giving 4.546 liters. The US gallon kept an older English wine gallon definition of 231 cubic inches - giving 3.785 liters. Two countries, two definitions, 20% difference.

Does the UK still use gallons?

Partially. UK fuel economy is officially quoted in miles per gallon (Imperial), and road signs show distances in miles. But fuel is sold by the liter at petrol stations. So a British driver buys fuel in liters but measures consumption in MPG. Canada switched fully to liters in the 1970s.

How do I convert MPG to L/100km?

For US MPG: divide 235.215 by the MPG value. Example: 30 MPG (US) = 235.215 / 30 = 7.84 L/100km. For UK MPG: divide 282.481 by the MPG value. Example: 30 MPG (UK) = 282.481 / 30 = 9.42 L/100km. The UK number is always higher because the Imperial gallon is larger.

Is a gallon of milk the same as a gallon of gasoline?

In terms of volume - yes, both are 3.785 liters (US). In terms of weight - no. Water weighs about 3.78 kg per US gallon, while gasoline weighs only about 2.72 kg per US gallon (because gasoline is less dense, with a specific gravity of roughly 0.72). A gallon is a volume measure, not a weight measure.

What is the quick way to estimate liters to gallons in my head?

Divide liters by 4 for a rough US gallon estimate (actual factor is 3.785, so you will be about 5% high). For UK gallons, divide by 4.5. Examples: 40 L is roughly 10 US gal (actual: 10.57). 60 L is roughly 15 US gal (actual: 15.85). Good enough for refueling decisions.

Related tools

Vehicle Weight Converter

Convert between kilograms, pounds and tons for vehicle weight specs - Open converter

Wheel Circumference Calculator

Calculate wheel circumference from tire size (e.g. 205/55 R16) and check speedometer accuracy - Open calculator

Fuel Consumption Calculator

Convert fuel consumption between L/100km, MPG and km/L across markets - Open calculator

Distance Converter

Convert kilometers to miles and back for odometers and route planning - Open converter

Engine Displacement Converter

Convert engine displacement between cc and liters with a reference atlas of real engines - Open converter