How Many Ounces In One Gallon?

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 an 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!

There are 128 US fluid ounces in a US gallon. If you’re in the UK, you’ll find a gallon measures 160 UK fluid ounces. This is due to the fact that the US liquid gallon is smaller than the UK imperial gallon (3.785 liters compared to 4.546 liters).

When converting gallons to ounces (fluid ounces), you should also bear in mind that the US fluid ounce is larger than the UK imperial fluid ounce. The US fluid ounce measures 29.5735mL. By comparison, the UK (imperial) fluid ounce measures 28.4131mL.

So, the US has a smaller gallon than the UK, but a slightly larger fluid ounce. It’s enough to cause your head to explode. When it comes to conversions between the two, here’s the info you need:

  • 1 Gallon (US) = 128 Ounces (US, Fluid)
  • 1 Gallon (UK) = 160 Ounces (UK, Fluid)

You should probably bear the size differences in mind if you’re considering changing your daily water intake because there’s a big difference between the two. You could be drinking 3/4 of a litre more water if you use the UK imperial gallon conversion.

How many ounces in one gallon

How Many Ounces Are In A Gallon Of Water?

In the US, a gallon of water measures 128 fluid ounces. In the UK, a gallon of water measures 160 fluid ounces. This is because the US and UK use different measurements for gallons and fluid ounces.

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:

Gallons To Ounces Conversions (US)

Gallons to fl oz (US)Gallons to fl oz (US)
1/4 gallon = 32 fl oz10 gallons = 1280 fl oz
1/2 gallon = 64 fl oz11 gallons = 1408 fl oz
3/4 gallon = 96 fl oz12 gallons = 1536 fl oz
1 gallon = 128 fl oz13 gallons = 1664 fl oz
2 gallons = 256 fl oz14 gallons = 1792 fl oz
3 gallons = 384 fl oz15 gallons = 1920 fl oz
4 gallons = 512 fl oz16 gallons = 2048 fl oz
5 gallons = 640 fl oz17 gallons = 2176 fl oz
6 gallons = 768 fl oz18 gallons = 2304 fl oz
7 gallons = 896 fl oz19 gallons = 2432 fl oz
8 gallons = 1024 fl oz20 gallons = 2560 fl oz
9 gallons = 1152 fl oz21 gallons = 2688 fl oz

Gallons To Imperial Fluid Ounces (UK)

Due to the fact that the UK uses the smaller imperial fluid ounce, conversions for UK gallons are as follows.

Gallons to fl oz (UK)Gallons to fl oz (UK)
1 gallon = 160 fl oz11 gallon = 1760 fl oz
2 gallons = 320 fl oz12 gallon = 1920 fl oz
3 gallons = 480 fl oz13 gallon = 2080 fl oz
4 gallons = 640 fl oz14 gallon = 2240 fl oz
5 gallons = 800 fl oz15 gallon = 2400 fl oz
6 gallons = 960 fl oz16 gallon = 2560 fl oz
7 gallons = 1120 fl oz17 gallon = 2720 fl oz
8 gallons = 1280 fl oz18 gallon = 2880 fl oz
9 gallons = 1440 fl oz19 gallon = 3040 fl oz
10 gallons = 1600 fl oz20 gallon = 3200 fl oz

How Many Ounces In A Gallon?


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.

How Many Gallons Does 64 Ounces Equal?

A gallon of liquid in the United States equates to 128 US fluid ounces. This means that 64 US fluid ounces measures the same as 1/2 a US gallon.

Is 1 Gallon The Same As 64 Oz?

No. A gallon of liquid contains 128 US fluid ounces. This means that half a gallon measures 64 US fluid ounces.

How Many 32 Oz Make A Gallon?

If you’re referencing the US gallon and US fluid ounce, 32 ounces equal one quart and equate to 1/4 of a gallon. You would therefore need 4 to make a US gallon.

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