How many Litres make a gallon in UK?

In the UK, a gallon contains 4.54609 litres. This means that 1 gallon is equivalent to approximately 4.55 litres. To convert between gallons and litres when dealing with liquid volumes in the UK, you can use a simple conversion ratio of 1 gallon = 4.54609 litres. This article will provide a more in-depth look at the relationship between gallons and litres in the UK measurement system.

The History of Gallons and Litres in the UK

Historically, a variety of different definitions of the gallon were used in England. In 1824, the Imperial Gallon was adopted as the standard gallon measurement, which contained 4.54609 litres. This was part of a broader effort to standardize weights and measures across the British Empire. The Imperial Gallon was defined as the volume occupied by 10 pounds of distilled water weighed at a temperature of 62°F with the barometer at 30 inches of mercury. This definition helped establish a consistent relationship between the gallon and the litre in the UK.

In 1965, the UK decimalized its currency and adopted the metric system for many measurements. Litres became a more commonly used unit than gallons. However, gallons remained an official unit used in the UK. The most common contexts where gallons are still frequently used are for measuring fuel efficiency in vehicles and beer or milk volumes. Although litres are now more widely used in day-to-day life, the Imperial Gallon remains the legally defined and measured gallon in the UK.

The Definition of a UK Gallon

The official current definition of the UK gallon is precisely 4.54609 litres. This is based on the Imperial Gallon, standardized in 1824, which contains 4.54609 litres by definition. All modern gallon measurements in the UK use this same conversion ratio. This exact figure enables easy conversion between gallons and litres with minimal rounding error.

The definition of a UK gallon is legally enforced by the Weights and Measures Act of 1985. This Act defines a gallon for trade purposes as 4.54609 litres exactly. It is illegal in trade contexts in the UK to use any other conversion factor between gallons and litres. This ensures consistency and accuracy in commercial volume measurements.

Key Facts About the UK Gallon

  • Contains exactly 4.54609 litres
  • Standardized in 1824 as part of Imperial system of weights and measures
  • Legally defined by the Weights and Measures Act of 1985 as 4.54609 litres
  • Used for measuring fuel, beer, milk, and some other liquid volumes
  • Less commonly used than litres in everyday measurements

This standardized definition allows for unambiguous conversions between gallons and litres in the UK measurement system.

Converting Gallons to Litres in the UK

To convert a volume measurement from gallons to litres in the UK, you simply multiply the number of gallons by 4.54609. This conversion ratio is based on the exact definition of a UK gallon as 4.54609 litres. Some examples of converting gallons to litres are:

  • 1 gallon = 4.54609 litres
  • 5 gallons = 22.73045 litres
  • 10 gallons = 45.46090 litres

This method allows you to accurately convert any measurement in gallons to the equivalent volume in litres in the UK system. The conversion is an exact one with no rounding required, thanks to the precise definition of the UK gallon.

Gallons to Litres Conversion Formula

The formula for converting gallons to litres in the UK is:

Litres = Gallons x 4.54609


  • Gallons is the volume in gallons
  • 4.54609 is the number of litres in 1 gallon
  • Litres is the volume in litres

You can use this simple formula to convert any measurement from gallons to litres accurately when dealing with liquid volumes in the UK.

Converting Litres to Gallons in the UK

To convert a volume measurement from litres to gallons in the UK, you divide the number of litres by 4.54609. This is because a UK gallon contains 4.54609 litres. Some examples of converting litres to gallons are:

  • 10 litres / 4.54609 = 2.197920947 gallons
  • 55 litres / 4.54609 = 12.09677536 gallons
  • 200 litres / 4.54609 = 43.99078014 gallons

When converting litres to gallons, you may need to round the results to the nearest hundredth or thousandth of a gallon to account for the division by 4.54609. Nonetheless, this method provides an accurate way to convert volume measurements from litres to gallons in the UK system.

Litres to Gallons Conversion Formula

The formula for converting litres to gallons in the UK is:

Gallons = Litres / 4.54609


  • Litres is the volume in litres
  • 4.54609 is the number of litres in 1 gallon
  • Gallons is the volume in gallons

You can use this simple formula to easily convert any liquid volume from litres to gallons in contexts where UK measurements are being used.

How Gallons and Litres Compare

Although both gallons and litres measure volume, they are based on different volumetric systems. Gallons are an Imperial unit, while litres are part of the metric system. One key difference is that a litre is defined as a base unit, while a gallon is defined based on the litre. Specifically, 1 gallon is defined as 4.54609 litres. This makes the gallon a derived unit.

Some key facts comparing gallons and litres include:

Measurement Gallon Litre
Volumetric system Imperial Metric
Unit definition 4.54609 litres Base SI unit of volume
Common uses Fuel, beer, milk (UK) General volume measurement

Although both can measure volumes, the gallon depends on the litre for its definition. The metric litre serves as the base unit that other volumes reference. This highlights the fundamental difference between these two units.

Why Gallons and Litres Are Used

Gallons remain in use for some specific applications in the UK, even though litres are considered the standard unit. There are a few reasons why gallons are still used in certain contexts:

  • Tradition – Gallons have historically been used to measure draught beer and milk. Pubs and dairies continue this tradition today.
  • Fuel efficiency – Miles per gallon (MPG) remains the standard measure of vehicle fuel efficiency in the UK.
  • Recipes – Some British recipes, especially for beers and ciders, specify volumes in gallons.
  • Consumer familiarity – Consumers are accustomed to seeing milk and beer sold by the pint, which is ~0.5 gallons.

However, litres are now the common unit for volume measurement in most everyday situations. Litres are generally preferred because:

  • They align with the International System of Units (SI).
  • They allow easier conversion between units (e.g., millilitres and cubic metres).
  • Decimal volumes are simpler for calculation than fractional Imperial volumes.

For most purposes, litres provide a standardized, convenient method of liquid measurement understood worldwide. But gallons remain useful in specific usage contexts with historical tradition.

Examples Comparing Gallon and Litre Volumes

To build familiarity and understanding of how gallon and litre volumes compare, it helps to look at some examples side-by-side:

Gallons Litres
1 gallon 4.54609 litres
5 gallons 22.73045 litres
10 gallons 45.46090 litres
0.5 gallon 2.2730 litres

This helps illustrate values like:

  • 1 gallon is over 4.5 litres
  • 0.5 gallon is 2.27 litres
  • 10 gallons is around 45 litres

With some practical examples, it becomes easier to develop an intuitive sense of how gallon and litre measures relate. This builds familiarity for converting between the two units.

Practical Applications and Conversions

Being able to accurately convert between gallons and litres is essential for many practical applications in the UK. Some common situations where gallon-litre conversions are useful include:

  • Cooking: Some British recipes may list volumes in gallons, requiring conversion to litres.
  • Shopping: Milk and beer are sometimes sold by the pint (~0.5 gallons) requiring conversion to litres.
  • Fuel economy: Converting MPG values to litres/100 km provides a standardized metric comparison.
  • Car capacity: Converting fuel tank capacity between gallons and litres.
  • Import/export: Converting product volumes during international trade.

For example, to convert a 50 litre fuel tank capacity to gallons, you would calculate:

50 litres / 4.54609 gallons/litre = 10.9918 gallons fuel tank capacity

Being able to carry out conversions like this is essential for seamless use of measurement values in different contexts. Familiarity with gallon-litre conversions facilitates commerce, transportation, cooking, and other applications.

Countries Using Gallons and Litres

While UK gallons are well-defined, gallon measurements vary between countries that use the Imperial system. The US gallon, for example, contains approximately 3.79 litres. The UK gallon is about 20% larger than the US gallon. Some other gallon definitions include:

Country Gallon Size
United Kingdom 4.54609 litres
United States 3.78541 litres
Canada 4.54609 litres (same as UK)
Australia 3.78541 litres (same as US)

So when converting gallons between different countries, you need to know which gallon definition is being used. The litre, meanwhile, has a consistent definition worldwide as an SI base unit. Any differences arise only when converting between gallons and litres across different countries.

The Importance of Consistent Definitions

Having precise, legally binding definitions for gallons and litres enables accurate conversions between volume units in the UK measurement system. When definitions drift or uncertainty arises, it can lead to mistakes and confusion over volumes in trade, cooking, transportation, and elsewhere. That is why standards like the Imperial Gallon in the UK and the litre worldwide are so important.

The UK Weights and Measures Act helps enforce consistent gallon and litre definitions. This reduces errors and ambiguities in commerce and daily use. When buying gallons of milk or litres of petrol, customers can feel assured they are getting the officially defined volumes. Shared definitions create a common language around measurement that facilitates economic and social activities.

As measurement systems evolve, maintaining precise definitions helps bridge old and new conventions. This way, traditions using gallons can continue while the metric system expands. Consistent gallon and litre definitions in the UK provide continuity, clarity, and precision for both historical and contemporary uses.

Changes in the UK’s Measurement System

While the UK gallon remains well-defined, there has been a broader shift away from Imperial units towards the metric system in recent decades. This transition aims to align the UK with the global standards of the International System of Units (SI).

Some key changes include:

  • Adopting metres, litres, grams, etc. for most everyday measurement purposes
  • Using metric units for retail and commerce
  • Teaching metric units in schools
  • Showing road distances and speed limits in miles and miles per hour, in addition to kilometres

However, Imperial units like gallons remain permissible for specific applications like draught beer and cider, milk sold in returnable containers, and vehicle fuel efficiency. The UK thus has a primarily metric measurement system today, with Imperial units still used in particular traditional contexts.

This hybrid approach provides continuity. Older generations comfortable with Imperial measures can continue using them, while newer generations adopt metric units. By retaining the gallon definition alongside the litre, the UK measurement system bridges historical conventions and modern standards.

The Gallon’s Ongoing Role and Value

Despite the increasing use of litres, the gallon still has an ongoing role and value in modern Britain. As a traditional unit, it preserves historical continuity in contexts like pub beer and milk delivery. Its continued legal definition also provides standards for trade and commerce. And the public is most familiar with fuel efficiency measures like miles per gallon.

The UK gallon does not need to be abolished for metrication to continue. Its precise definition in terms of litres means it can coexist seamlessly. The gallon can remain in situational use where it provides value, while metric units handle most day-to-day measurement needs. This demonstrates the ounces of flexibility a well-integrated measurement system can offer.

So don’t worry, you will still be able to order your next few pints down at the pub in gallons! Just remember there are about 4.54609 litres to each gallon and you’ll stay nicely calibrated between traditional and modern conventions. The gallon remains a pint-sized part of the UK’s rich measurement history.


In the UK measurement system, 1 gallon contains exactly 4.54609 litres. This Imperial Gallon definition standardizes the conversion ratio between gallons and litres. The UK Weights and Measures Act legally enforces this definition to ensure consistent trade measurements.

Converting between gallons and litres simply requires multiplying or dividing by 4.54609. Although litres are now more widely used in everyday life, gallons remain important for applications like fuel efficiency, draught beer and cider, and milk. Having precise gallon and litre definitions facilitates commerce and reduces confusion while allowing historical traditions to continue.

Understanding the relationship between gallons and litres, and being able to accurately convert between them, is essential for many practical purposes in the UK. The definitions provide continuity between old Imperial measurements and the modern metric system. As the UK transitions towards greater metrication, its standardized gallon and litre units help maintain coherence, precision, and clarity in measurement.

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