Are you wondering how many ounces in a gallon? It isn't easy to remember how to convert liquid oz to a gallon or gallons to ounce. You'll need to do a little basic math. But don't worry, I've done it all for you, including a conversion chart!
Have you ever wondered how many ounces in a gallon or half a gallon?
In this blog post, we will explore the different measurements that are used to measure volume, and what is a gallon.
You'll also learn about how to convert between these Imperial and metric units of measurement!
Whether you're cooking, doing science, or working on a project, sometimes you need to make some conversions.
I know how hard it can be when you're cooking and your favorite recipe is written in Imperial, but you know Metric or vice versa.
Suddenly you might find that you're racking your brain to remember how many oz in a gallon?
There isn't a very straightforward answer, but don't worry! I've done all the conversions and calculations for you.
Just keep scrolling down and I've done all the conversions for you!
I've also made a handy free printable (get it below) full of kitchen conversions! Just print it out and keep it with your cookbooks.
Ounces can be confusing, so I also have a handy guide if you're wondering How Many Ounces in a Quart? Or How many cups in a pint, quart or gallon.
It might also help you to check out this guide to Imperial vs Metric.
Jump to:
What is a gallon?
A gallon is a measure of volume and fluid in both British Imperial units and US Customary units. Three significantly different sizes are in current use:
A gallon equals 4 quarts, 8 pints, or 128 fluid ounces.
Abbreviation for gallon: gal.
The word "gallon" has its roots in the latin word, "galleus" or "galena", meaning container or large jar and was originally used as a measurement of wine production.
A commonly used volume measure in the United States is gallons. There are four quarts in a gallon and 128 fluid ounces in a gallon. A quart is made up of two pints or four cups, and there are three cups in a pint. One cup equals eight fluid ounces so one pint equals 16 fluid ounces.
The Imperial system uses the same measurements as the Metric system except that it doesn't use liters instead it goes with gallons but they have different names like barrels (UK) or hogsheads (US).
For the purposes of this conversion, I'll be using the US customary system.
What is an ounce?
An ounce is a unit of weight (dry ounce) or a unit of volume (fluid ounce).
A fluid ounce (fluid oz.) is a unit of measurement for both liquid and dry ingredients and is commonly used in cooking, baking, nutrition and pharmacies.
Abbreviation: fl oz, fl. oz., or oz. fl.
There are very slight differences in the conversions for Imperial or US Customary measurements.
US: 1 fluid ounce = 29.6 ml
UK: 1 fluid ounce = 28.4 ml
Ounces can be abbreviated to oz.
In recipes, you might also see fluid ounces abbreviated to fl oz.
A fluid ounce is a unit of liquid volume equal to ⅛th of a pint or 1/32nd of a quart.
General Conversions
To get started, here are the usual conversions for liquids:
USA conversion: 1 US fluid quart = 2 pints = 4 cups = 32 fluid ounces = 950 mililitres.
1 gallon = 4 quarts
UK conversion: 1 Imperial quart = 40 Imperial fluid ounces = 4+¾ cups = 1.13 litres.
1 gallon = 4 quarts = 8 pints = 16 cups = 128 fluid ounces
Half gallon of water contains 64 US fluid ounces.
Mathematical Formula
To convert fluid ounces to gallons and vice versa, you need to divide the volume by the conversion ratio.
In order to convert from gallons into ounces, multiply your number by 128 (or divide it by 128 if you want the answer in ounces)
Fluid ounces in a gallon:
1 gallon = 128 fluid ounces, so the formula is:
x fluid ounces ÷ 128 = x gallons
Ounces to Gallons
1 US Fluid Ounce = 0.0078125 fluid gallon, so the formula is:
x gallons x 128 = x fluid ounces
In other words:
Convert fluid ounces to gallons = the oz x 128.
Convert gallons to ounces = the gallons ÷ 128.
Ounces to Gallons
"How many ounces in a gallon?" This is one of the most common questions asked about liquid measurements.
A gallon is equal to 8 pints, 4 quarts, or 16 cups. There are 128 fluid ounces in a gallon and this number will differ depending on whether you use Imperial or Metric measures.
Now you know what gallons and ounces are, as well as the mathematical conversion equations.
So, let's get on to the conversions. I'm sure you're still wondering how many ounces per gallon of water, or half a gallon!
I've broken it down below:
NOTE: All conversions below are in US liquid measures.
How many ounces in half a gallon?
There are 64 fluid ounces in ½ gallon.
How many ounces in 1 gallon?
There are 128 fluid ounces in 1 gallon.
How many oz in 2 gallons?
There are 256 fluid ounces in 2 gallons.
How many oz in 3 gallons?
There are 384 fluid ounces in 3 gallons.
How many oz in 4 gallons?
There are 512 fluid ounces in 4 gallons.
How many oz in 5 gallons?
There are 640 fluid ounces in 5 quarts.
Fluid Ounces to Gallons Chart
Use this handy chart to easily see how many fluid ounces are in a gallon. Note that Fl oz. measurements are rounded.
| US Gallon | US Fl oz |
| ¼ gallons | 32 fl oz |
| ½ gal | 64 fl oz |
| 1 gal | 128 fl oz |
| 2 gal | 256 fl oz |
| 3 gal | 384 fl oz |
| 4 gal | 512 fl oz |
| 5 gal | 640 fl oz |
| 10 gal | 1280 fl oz |
Printable chart
Want a FREE handy kitchen conversion chart? I've got you covered! This chart will help you with lots of cooking conversions. Enjoy!
Click to download and print this kitchen conversion chart.
Be sure to also check out my handy Vegan Grocery Shopping List.
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