About the Gallons to Liters Calculator
Gallons appear on American fuel pumps, milk jugs, paint cans, water heaters and pool specifications, and on older British records and some fuel economy figures as the larger imperial gallon. Most of the world measures the same things in litres. To compare a US fuel price with a local one, understand a water heater's capacity or dilute a garden product correctly, gallons need converting to litres — and it matters which gallon you start from.
This gallons to liters calculator converts US gallons or UK (imperial) gallons to litres exactly. It also shows the volume in millilitres and cubic metres, the equivalent in the other kind of gallon, and, if you enter a price per gallon, the price per litre.
How to Use the Gallons to Liters Calculator
Enter the number of gallons.
Choose US gallon or UK (imperial) gallon. American sources use US gallons; British sources, particularly older ones, use imperial gallons.
Optionally, enter a price per gallon to see the price per litre.
The Formula
litres = US gallons × 3.785411784
litres = UK gallons × 4.54609
price per litre = price per gallon ÷ litres per gallonBoth factors are exact. The US gallon is defined as 231 cubic inches; the imperial gallon as 4.54609 litres.
Step-by-Step Example
10 US gallons.
10 × 3.785411784 = 37.8541 LSo 10 US gallons is 37.8541 litres, or 8.32674 imperial gallons.
10 UK gallons is 10 × 4.54609 = 45.4609 litres, about 12.0095 US gallons.
Fuel at 3.50 per US gallon costs 3.50 ÷ 3.785411784 = 0.92 per litre in the same currency.
Quick Reference
1 US gal = 3.78541 L 1 UK gal = 4.54609 L
5 US gal = 18.9271 L 5 UK gal = 22.7305 L
10 US gal = 37.8541 L 10 UK gal = 45.4609 L
20 US gal = 75.7082 L 20 UK gal = 90.9218 L
50 US gal = 189.271 L 50 UK gal = 227.305 LUS and Imperial Gallons
The two gallons have different histories. The US gallon comes from the English wine gallon of 231 cubic inches, used before American independence. In 1824 Britain replaced its various gallons with a single imperial gallon, defined as the volume of 10 pounds of water, which is larger. So one imperial gallon is about 1.2 US gallons, and one US gallon about 0.833 imperial gallons. Canada and some Caribbean nations used imperial gallons before going metric, which is why older fuel figures from those countries use the larger gallon too.
Water Heaters, Pools and Tanks
American water heaters are typically 40 to 80 US gallons, about 151 to 303 litres. A backyard pool of 15,000 US gallons holds about 56,800 litres, or 56.8 cubic metres, useful when buying chemicals dosed per 10,000 litres. A 55-gallon drum, a common industrial container, holds 208.2 litres.
Fuel Prices and Consumption
Converting a US price per gallon to a price per litre, and then to your currency, gives a fair comparison with local fuel prices. The same factor applies to fuel use: a car that burns 10 US gallons on a trip used 37.85 litres. For fuel economy figures such as miles per gallon, which are ratios rather than volumes, use a fuel economy converter instead.
Milk and Drinks
In the US, milk is sold by the gallon, half gallon and quart. A US gallon of milk is 3.785 litres, a half gallon 1.893 litres, and a quart 946 millilitres, close to the 1-litre cartons common elsewhere. In the UK, milk is sold in pints of 568 millilitres, with a 4-pint bottle holding 2.273 litres, exactly half an imperial gallon.
Dilution and Mixing
Garden chemicals, cleaning concentrates and pool treatments often give a dose "per gallon of water". Converting to litres makes the dose easy to measure with metric jugs: a dose of 2 fluid ounces per US gallon is about 59 ml per 3.79 litres, or 15.6 ml per litre. If the instructions come from Britain and mean imperial gallons, the same dose per gallon is spread over 4.55 litres, so the mixture is weaker per litre. Getting the gallon right matters most for strong chemicals, where too high a concentration can damage plants, surfaces or skin.
Rain and Water Use
Water use is reported in gallons in the US and litres or cubic metres elsewhere. A typical American household uses around 300 US gallons a day, about 1,136 litres. A five-minute shower at 2.5 US gallons a minute uses about 47 litres, and a dishwasher cycle of 4 US gallons about 15 litres. Converting both figures to the same unit makes comparisons with water bills, which are usually priced per cubic metre outside the US, straightforward.
Understanding Your Result
The headline is the volume in litres.
The millilitres line gives the volume in millilitres and cubic metres.
The other gallon line gives the same volume in the other kind of gallon.
The price per litre line converts a price per gallon, if you entered one.
When Should You Use This Calculator?
Use it to compare US fuel prices with prices per litre.
Use it for water heater, pool and tank capacities in gallons.
Use it for paint, chemicals and garden products with gallon instructions.
Use it for older British or Canadian figures in imperial gallons.
Common Mistakes
Using the wrong gallon. Check whether the source is American or British.
Converting mpg with this calculator. Fuel economy needs a different conversion.
Dividing instead of multiplying. From gallons to litres, multiply.
Mixing US and UK pints or quarts. Their sizes differ like the gallons.
Rounding to 4 litres a gallon. That is about 6 percent high for US gallons.