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Need to know how many ounces are in a gallon? I’ll break it down for you with terms, fun facts, and a handy conversion chart!
Knowing how many ounces are in a gallon can come in handy, whether you’re in the middle of a recipe, working on a project, or trying to settle a bet with friends.
The shortest answer is that there are 128 ounces in one gallon, BUT it’s not that simple. The exact measurement can differ depending on where you live, so I created a chart that explains everything you could ever want to know (so you might not lose that bet after all!).
Table of Contents
How many ounces are in a gallon?
Short answer: there are 128 fluid ounces in a gallon.
However, it can vary depending on liquid or dry gallons and the system of units used. One dry US gallon is equal to 148.94545 ounces.
If you use the British Imperial system, then there are 153 Imperial fluid ounces in 1 Imperial gallon.
An important point to note is that the United Kingdom only uses the British Imperial system for gallons. For almost all other measurements, they use the metric system (for example, measuring how many ounces are in a cup).
How to convert ounces to gallons
The formulas for converting ounces to gallons differ depending on whether you use the metric or US customary systems. The following conversion formula is useful if you have metric units.
Metric conversion = fluid ounces ÷ 128
If you are dealing with the Imperial conversion system, the following formula will be used to find gallons:
Imperial conversion = fluid ounces ÷ 153
Here is a helpful conversion chart for liquid measurements:
| 8 fl oz | 1 cup | 1/2 pint | 1/4 quart | 1/16 gallon |
| 16 fl oz | 2 cups | 1 pint | 1/2 quart | 1/8 gallon |
| 32 fl oz | 4 cups | 2 pints | 1 quart | 1/4 gallon |
| 64 fl oz | 8 cups | 4 pints | 2 quarts | 1/2 gallon |
| 128 fl oz | 16 cups | 8 pints | 4 quarts | 1 gallon |
What is a gallon?
The term ‘gallon’ likely originated from the medieval Latin word ‘galleta,’ meaning jug. Today, it’s used as a unit of volume in the US measurement system, specifically for holding large quantities of liquids. It’s often abbreviated as ‘gal.’
In US measurements, one gallon of water equals 3.785 liters and weighs about 8.34 US pounds.
What is an ounce?
The term ‘ounce’ originates from the ancient Roman word ‘uncia,’ meaning one-twelfth of a Roman pound, a type of currency. Now, it’s used as a unit of measurement for dry goods and liquids (the latter is measured by liquid ounces).
There are two types of ounces: fluid ounces (fl oz) and dry ounces. One US fluid ounce weighs 1/16th of a US pound or 28.3 grams.
Measuring ounces and gallons internationally
Now that you know there are 128 ounces in a gallon, let’s see how to measure it outside of the United States.
Using the British Imperial system, 1 UK gallon equals 1.2 US gallons or 153.6 fluid ounces. Many changes have occurred in the Imperial gallon over time, and the value has changed anywhere between 129 to 163 ounces.
In Canada, New Zealand, Australia, and South Africa, the metric system is more common than Imperial gallons and ounces. In the United States, the Imperial system is used for almost everything.
Wet vs dry gallons
Yes, believe it or not, there are more than just two types of gallons. Wet gallons and dry gallons are NOT the same, as dry gallons factor in volume and are much larger than wet gallons.
Dry gallons measure dry goods like grains, flour, or fruit. One dry gallon equals ⅛ of a bushel or 231 cubic inches. Luckily this unit of measurement for dry ingredients is rare, so you shouldn’t come across this often.
The general conversion is the same for both dry and wet gallons, and you get 4 quarts in a gallon, 2 pints in a quart, and 2 cups in a pint.
Fluid ounces vs dry ounces
If you were to look at 8 ounces of blueberries versus 8 ounces of blueberry juice, you’d notice the difference is quite extreme! Here are some handy units of measurement for dry ounces:
1 dry ounce = 1/16 US pound
4.5 dry ounces = 1 US cup
Frequently asked questions
You would need 4 32 oz. bottles of water to equal one gallon.
There are 16 8 oz cups in one gallon.
