This guide will help you thoroughly understand the relationship between gallons and liters, master precise conversion methods, and learn how these units are used in real life.
Imperial gallons are approx. than US gallons20.04%. This means that if you mistakenly calculate a US gallon as an Imperial gallon, the result will be about one-sixth off; otherwise, the result will be about one-sixth off. In scenarios involving large amounts of liquid, this error can be significant.
When you don't need exact values, you can use the following approximate formula for mental arithmetic:
燃油效率的单位在不同国家差异很大。美国使用MPG（英里/加仑），而中国和欧洲使用L/100km（升/百公里）。如果你在美国租车或看汽车评测，需要将MPG转换为更熟悉的升/百公里。
For example, a car's fuel consumption is 30 MPG (US), which is equivalent to 235.215 ÷ 30 =7.84 L/100km。
Many recipes from the United States or the United Kingdom use units of volume such as gallons, quarts, and pints. Knowing the conversion relationship can help you accurately restore recipes.
For example, a recipe calls for "1.5 gallons of water" (US), you would need 1.5 × 3.785 =5.68 literswater. If calculated in imperial units, this is 1.5 × 4.546 =6.82 liters, the difference is more than 1 liter!
When purchasing pool chemicals or calculating fill time in the United States, pool capacity is usually measured in gallons. You can use the following formula to convert.
例如，一个20英尺 × 40英尺、平均深度5英尺的泳池：
Aquarists often need to convert between different units. U.S. fish tank capacities are usually listed in gallons, while domestic fish tanks are listed in liters.
The history of the gallon dates back to medieval England. The word "gallon" is derived from the Old French "galon" and was originally used to measure the volume of wine and ale. Because different products require different containers, there have historically been standards for "wine gallons," "beer gallons" and "corn gallons."
In 1824, the British passed the Weights and Measures Act, which unified the imperial gallon to the volume of distilled water occupying 10 pounds of weight at 62°F. The United States, on the other hand, retained the standard based on the old imperial wine gallon, resulting in the two-gallon system we see today.
This is because the United States retained the old imperial "wine gallon" standard used during the colonial period (231 cubic inches) after independence, while the British redefined the gallon standard in 1824 (the volume of 10 pounds of distilled water). The two countries embarked on different paths to standardization, and the differences continue to this day.
Canada officially switched to the metric system in the 1970s, using the liter as the standard unit for daily use. However, in some informal situations, especially among older people and some industries, the imperial gallon is still mentioned. Canada has never used US gallons.
Depends on vehicle origin. American brands and vehicles sold in the United States use US gallons; British brands (eg Jaguar, Land Rover) may use Imperial gallons in Commonwealth markets. Check your vehicle manual or local regulations to confirm specific standards.
美制单位体系中还存在一个"干量加仑"（US dry gallon），等于 1/8 蒲式耳，约 4.405 升。它用于测量干性物品（如谷物、水果）的体积，但在日常生活中极为罕见，绝大多数情况下的"加仑"指的都是液体加仑。
The most reliable way is to look at the source: information from the United States is in US gallons, and information from the UK, Canada or Australia is in Imperial gallons. If unsure, the US gallon is a safer default choice as it is more commonly used in the international media and on the internet.
The conversion of gallons to liters may seem simple, but the difference between the American and British standards is an easy pitfall. Getting the wrong gallon type can lead to significant errors in fuel economy comparisons, recipe restoration, pool management, and more. Memorizing the core conversion factors—US 3.785, British 4.546—can handle most daily needs.
Need an exact conversion? try our