A gallon is a unit of volume for liquids. It is used both in the United States system of measurements, United States customary units, and in the Imperial measurement system.
Both measurement systems have their routes in much older British systems of measurement.
Although the term is regularly used as a unit of measurement for water, many of us don’t really have much sense of how much a gallon of water is.
This is especially important in terms of understanding your personal water usage.
You might read that the average person uses 80-100 gallons of water a day, but what does that mean in real-world terms?
Luckily for you, you’ve come to the right place to improve your knowledge of the humble gallon.
In this article, we’ll be trying to give you an idea of how much a gallon of water is.
How Much Is A Gallon?
Historically, there were several different definitions of what constituted a gallon.
These differing gallons were one of the main forms of liquid measurement in the British Isles before eventual standardization in the 19th century.
Different types of gallons over the centuries include the Winchester or corn gallon at 157 imperial fluid ounces, the Old English (Elizabethan) ale gallon at 163 imperial fluid ounces, and the Irish gallon at 125 imperial fluid ounces.
In the modern day, just two definitions of gallon have survived.
One is the gallon measurement of the Imperial system, whilst the other two are found in the U.S. customary system.
The imperial gallon, still used in some Commonwealth countries, is defined as exactly 4.54609 cubic decimeters.
In other words, there are just over 4.5 liters in an imperial gallon.
There are 4 quarts in a gallon and 2 pints in a quart, meaning that there are 8 pints in a gallon.
In metric terms, Each pint measures 0.56826125 liters exactly, but is commonly referred to as 568ml. Each imperial pint consists of 20 fluid ounces.
Given a pint is an eighth of a gallon, that means there are 160 fluid ounces in an imperial gallon.
U.S. Liquid Gallon
Frequently referred to simply as a ‘gallon’ in the United States, the US liquid gallon is the American equivalent of the Imperial gallon.
The US liquid gallon has a strict legal definition, which is given as 231 cubic inches. This is exactly 3.785411784 liters.
As with the imperial gallon, there are four quarts in a gallon and two pints in a quart.
Where the US system departs from the imperial system is the number of fluid ounces in a pint.
Where the imperial system has 20, there are just 16 US fluid ounces in a US pint. This means that there are 128 US fluid ounces in a US liquid gallon.
U.S. Dry Gallon
The dry gallon is often forgotten because it is never actually used in the US customary system.
Indeed, many use the National Institute of Standards and Technology handbook as their official authority on measurement law, and the dry gallon is not included.
Nevertheless, it implicitly exists, since the dry measurements of bushel, peck, quart, and pint are still used.
The dry gallon was originally one-eighth of a bushel. It measured 268.8025 cubic inches, which is 4.40488377086 liters exactly.
So, that’s the technical part done. But what do gallons look like in everyday situations?
It’s the best way for people to visualize exactly how much a gallon of water is.
Let’s look at glasses first, and for our purposes we’ll obviously be sticking with US gallons.
Gallons As Glasses
A standard-sized glass of water holds eight fluid ounces.
Since a gallon contains 128 fluid ounces, one gallon of water is equivalent to 16 standard glasses of water.
Since a pint glass should hold 16 ounces of water, a gallon of water would be made up of 8 full pint glasses of water.
A typical lowball glass contains about 4-6 fluid ounces.
Therefore, 32 4 fluid ounce glasses would equal a gallon, as would roughly 21 and a bit (21.3) 6 fluid ounce lowball glasses.
Gallons As Bottles
The average standard-sized, single-use water or soda bottle in the United States is 16.9 fluid ounces.
Given there are 128 ounces in a gallon, completing a basic bit of division leads you to find that there are just over seven and a half (7.574) 16.9 fluid ounce bottles of water in a gallon.
Gallons As Fast Food Drink Sizes
Another good way to think of gallons is fast food drink sizes.
At Mcdonald’s, for example, the drinks are served in small (16 oz), medium (21 oz), and large (30 oz) cups.
That means that even a small drink is equivalent to a pint, which means 8 small Mcdonald’s drinks equals a gallon.
Just over 6 medium-sized drinks are equivalent to a gallon (6.0952), whilst four and a bit large drinks (4.2666) also equal a gallon.
Gallons Around The House
The average kitchen sink holds about 15-20 gallons of water, depending on its size.
The average bathtub holds about 80 gallons of water when full.
Smaller tubs can hold roughly 40 gallons, whilst the largest out there can hold up to 110 gallons.
A typical bath- that is, when the bath isn’t full to the brim- uses about 35-50 gallons of water. You could also think about gallons in terms of buckets.
A small bucket holds a gallon of water, a medium bucket will hold 2 gallons, whilst a large bucket will hold up to 5 gallons of water.
There are approximately 660,430 liquid gallons of water in an Olympic swimming pool.
Assuming the average American uses about 3,000 gallons of water per month, that is equivalent to about 18 and a half years of a single person’s water usage.
The rate of flow over Niagara Falls is 37 million gallons per minute.
Understanding the size of a gallon is important for developing an understanding of our personal water usage.
Hopefully, this article, with its technical definitions of a gallon and examples of gallons in real-world measurements has given you a sense of the size of a gallon of water.