A half US gallon is equal to 64 US fluid ounces. A gallon is the same size as four US quarts, eight US pints, or sixteen US cups. A US customary cup is eight US fluid ounces.

In the British imperial system of measuring, 1 imperial gallon is equal to 160 imperial fluid ounces. This means that 64 imperial fluid ounces are equal to about 0.40 imperial gallons.

Most measurements in the US customary system and the English system are the same, but the way liquids are measured is a little different. Read on to learn how to measure ounces, gallons, and other units in both systems, as well as how to use the metric system.

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## The units of measurement used in the US

The old English system is a good deal of what the US customary units of measurement are based on. This way of measuring dates back to the time of the Anglo-Saxons, which was around the year 450 AD. Most of the units of measurement used in the US customary system came from this time. This includes the inch (or ynce), which is equal to three barleycorns, and several units of the foot, which are equal to 12 or 13 inches. When the Normans took over England in 1066, they added new units of measurement like the rod and the furlong.

The first colonists brought the English way to the Americas. Even after the American War of Independence, it didn’t go away. But Holland, Spain, and France also had an effect on the way people in the US measure things. This made it hard for the colonists to understand because some of the measurements were different from state to state.

After America got its independence, the states were able to come up with a standard way to measure weight and length. This was the start of how people in the US measure things. By 1821, John Quincy Adams, who was then the US Secretary of State, had looked into the units of measurement used in 22 states. He came to the conclusion that the measurements are close enough that no changes or adjustments were needed.

## The British Imperial System vs. the US Customary Units

In 1824, the British imperial system was made uniform. Most units of length, area, and weight stay the same between the US customary system and the imperial system. When it comes to measuring volume, however, the US customary units and the British imperial units are very different. See how millilitres from the metric system are used to compare the two systems.

1 US fl oz = 29.573 ml

1 imperial fl oz = 28.412 ml

1 US pint = 473.176 ml

1 imperial pint = 568.261 ml

1 US quart = 946.353 ml

1 imperial quart = 1,130.52 ml

1 US gallon = 3,785.41 ml

1 imperial gallon = 4,546.09 ml

In the US customary system, 1 US fluid ounce is slightly bigger than 1 imperial fluid ounce. So, 64 US fl oz is a bigger amount of liquid than 64 imperial fl oz.

## How many Metric System Units are in half a gallon?

Most countries in the world have switched to using the metric system to measure things. This system is built around the number 10. Each additional unit adds or subtracts a power of 10. In the metric system, a centilitre is 10 millilitres, a deciliter is 10 centilitres, and a litre is 10 deciliters.

A US fluid ounce is equal to 29.573 ml. So, 64 US fl oz, or half a US gallon, is about 1.892 litres or 1,892.67 ml. A fluid ounce in imperial is equal to 28.413 millilitres. This means that in the metric system, 64 imperial fl oz is equal to about 1,818.43 ml or 1.81 litres.

## Why it’s important to know the difference between the different units of measurement

There are times when it helps to have a general idea of how the US and imperial units for measuring volume differ. For example, if a recipe was written for a British audience, you’ll know that the amounts will be a little different in US measurements. In the same way, the number of miles per gallon a car gets will change depending on how it is measured.

## Converting Between Systems

Having a handy converter app on your phone or tablet is one of the easiest ways to deal with the different ways people measure things. All you have to do is type in the number in the system you don’t know, and the app will change it to the system you prefer.

Dealing with different ways to measure things when cooking can be frustrating. Having a digital kitchen scale that you can count on and that can instantly change units will make things easier for you. If you don’t trust the scales, it will be even better to have measuring cups for all three units of volume.

##### The Daily Buzz Team

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