How much is a gallon of water in mL UK?

In the United Kingdom, a gallon of water is equivalent to approximately 4546 milliliters (mL). This conversion can be useful for recipes, DIY projects, gardening, and any application where knowing the metric volume of a gallon is needed.

Quick Conversion

Here is a quick overview of the gallon to milliliter conversion:

  • 1 gallon = 4 quarts
  • 1 quart = 2 pints
  • 1 pint = 20 fluid ounces
  • 1 fluid ounce = 28.41 mL

So one gallon contains 4 quarts x 2 pints x 20 fluid ounces x 28.41 mL which equals approximately 4546 mL.

The Gallon Unit of Measurement

The gallon is a unit of volume used in both the imperial and United States customary measurement systems. There are several different definitions for the gallon depending on where it is being used:

  • Imperial gallon (used in the UK and some other countries) – approximately 4.546 liters
  • US liquid gallon (used in the US) – approximately 3.79 liters
  • US dry gallon (used in the US) – approximately 4.40 liters

The imperial gallon, which is used in the United Kingdom, is the definition we will use for this conversion since the question specifies “UK.”

The Imperial Gallon

The imperial gallon is a unit equal to 4.546 liters or 277.42 cubic inches. It is about 20% larger than the US liquid gallon. The imperial gallon is divided into 4 quarts, 8 pints, or 160 fluid ounces.

The imperial gallon was originally defined as the volume occupied by 10 pounds of water at 62°F. It was later redefined in the UK Weights and Measures Act of 1985 as exactly 4.546 liters making it align with the metric system. It is still routinely used in the UK for measuring fuel, draught beer, milk, and some other liquids.

Converting Gallons to Milliliters

To convert from gallons to milliliters, we need to use the following conversion:

1 imperial gallon = 4.546 liters

And since 1 liter is equal to 1000 milliliters, we can calculate:

1 imperial gallon = 4.546 liters x 1000 milliliters/1 liter = 4546 milliliters

So in the UK, 1 imperial gallon is equivalent to approximately 4546 mL.

Converting Other Volumes

Using the same conversion factors, we can convert between other imperial units and milliliters:

  • 1 quart = 1136 mL
  • 1 pint = 568 mL
  • 1 fluid ounce = 28.41 mL

Converting Milliliters to Gallons

We can also convert in the opposite direction, from mL to gallons. To do this, we use the same conversion factor but invert it:

1000 milliliters = 1 liter

4.546 liters = 1 imperial gallon

So to convert milliliters to gallons, we divide the number of milliliters by 4,546 to obtain the equivalent number of gallons.

For example:

10,000 mL / 4,546 = 2.2 gallons

50,000 mL / 4,546 = 11 gallons

Examples of Gallon to Milliliter Conversions

Here are some examples of converting imperial gallon measurements to milliliters:

Gallons Milliliters
1 gallon 4,546 mL
2 gallons 9,092 mL
5 gallons 22,730 mL
10 gallons 45,460 mL

To convert any number of gallons to milliliters, simply multiply the gallons by 4,546.

Using the Conversion in Recipes and Projects

Knowing the milliliter equivalent of gallon measurements is useful for recipes and DIY projects that use metric volumes rather than imperial units. Here are some examples:

Recipe Example

A bread recipe calls for 2 gallons of water. How much is that in milliliters?

2 gallons x 4,546 mL/gallon = 9,092 mL

So 2 gallons translates to 9,092 milliliters of water for the bread recipe.

DIY Project Example

You purchase 5 gallons of paint for a DIY home project. How many milliliters is this to properly estimate the number of coats needed?

5 gallons x 4,546 mL/gallon = 22,730 mL

So 5 gallons of paint equals 22,730 milliliters which will help estimate the coverage in m2 when painting.

Why Convert Between Gallons and Milliliters?

There are several reasons why you may need to convert between gallons and milliliters in everyday situations:

  • Following recipes from different regions – Recipes from Europe or other metric regions may use milliliters instead of gallons for volumes.
  • Buying paint for DIY and construction projects – Paint coverage is often estimated in milliliters but paint is sold in gallons.
  • Understanding fuel economy – In Europe, fuel efficiency for vehicles is measured in liters/100 km rather than miles/gallon.
  • Calculating water usage – Water meters may measure in gallons while recommendations or regulations are given in liters or milliliters.
  • Fitting suitcases – Airlines may limit check-in luggage by fluid ounces or liters while suitcase sizes are described in gallons.

Being able to quickly convert between the two units allows you to work seamlessly between metric and imperial measurement systems used in different contexts.

Other Unit Conversions

In addition to converting between gallons and milliliters, you may also need to convert between other imperial and metric units. Here are some of the most common conversions:

  • Weight
    • 1 pound (lb) = 453.592 grams (g)
    • 1 ounce (oz) = 28.3495 g
  • Length
    • 1 inch (in) = 2.54 centimeters (cm)
    • 1 foot (ft) = 0.3048 meters (m)
    • 1 mile = 1.609 kilometers (km)
  • Volume
    • 1 pint (pt) = 473.176 milliliters (mL)
    • 1 quart (qt) = 0.946 liters (L)
    • 1 fluid ounce (fl oz) = 29.57 mL

Many more unit conversions are useful to know when converting between imperial and metric units. Having a handy reference guide or converter tool can help make these translations easy.


In summary, a gallon of water equals approximately 4,546 milliliters in the UK imperial system. This conversion can be useful for converting between recipes, product volumes, DIY project measurements, and other applications using US customary gallons versus metric milliliters.

The process is straightforward:

  • 1 imperial gallon = 4.546 liters
  • 1 liter = 1000 milliliters
  • So 1 gallon = 4,546 mL

Knowing important conversions like gallons to milliliters allows seamless transitions between imperial and metric units. With a handy reference or converter tool, gallons can easily be translated to milliliters and other important units like pounds to kilograms when needed.

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