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How Many Ounces In A Gallon? (Calculator and Conversion Chart)

Last Updated on November 2, 2023

Wondering how many ounces are in a gallon? Do you have trouble figuring out how many ounces in a gallon? You are not alone!

To make matters worse, it also depends on whether you’re talking about the US customary system or the British imperial system.

So, join us as we dive deep into the mysterious and often confusing world of units of measurement!

how many oz in a gallon

It’s an important question — and one that has baffled home cooks and professional bakers when measuring gallons of water or gallons of milk!

Luckily, we’ve got you covered. In this blog post, we’ll provide a straightforward guide to help you easily convert US gallon and US fluid ounces – no math required!

How many ounces in a gallon?

First, knowing the basics of measurement and unit conversion is useful skill both in everyday life and when cooking and baking. 

If you understand how many fluid ounces are in a gallon will not only help you when measuring liquids but also when you want to figure out how many cups or pints are equivalent to a gallon.

The answer is 128 US fluid ounces = 1 US Gallon

Gallon to Fluid Ounces Conversion Calculator

Gallon to Fluid Ounces Conversion Calculator


How to convert fluid ounces into one gallon?

Furthermore, understanding liquid measurements is essential in math-related activities and day-to-day life.

In the United States, people measure liquid by using gallons and quarts, which can be confusing at times.

A gallon is a large unit of liquid measurement that is equal to 128 fluid ounces. This means there are 128 fluid ounces per U.S. gallon of liquid.

To make it easier to visualize how many ounces are in a gallon, refer to the following table for quick reference:

GallonFluid Ounces
1 Gallon128 fl oz
1/2 Gallon64 fl oz
1/4 Gallon32 fl oz

US Customary Unit of Measurement (USCS or USC

In the United States and other countries that use United States customary units, a gallon is equal to 128 fluid ounces.

This measurement system is different from the metric system, which is widely adopted by many other countries around the world.

The gallon is for measuring both dry and liquid foods and beverages, as well as gasoline and other items.

In the case of liquids such as water and milk, manufacturers often use quarts or pints instead of ounces to measure a gallon.

A standard U.S. size gallon holds 4 quarts, 8 pints, or 128 ounces; providing convenience when attempting to quantify large amounts of liquid or dry material with commonly found measuring cups or containers around the home. 

There are also smaller measurements including a “half a gallon” which contains 64 ounces, and a “quart” which holds 32 ounces, both still falling under the U.S. customary unit measurement system for gallons.

blue large water bottles

It’s possible to measure larger amounts of liquid using 5-gallon buckets such as those found in most home improvement stores.

These buckets typically hold 640 ounces; an amount roughly equivalent to 1/2 flat-topped bushel baskets which are frequently used for storage purposes on farms across rural America.

What is an ounce (oz.)?

The ounce (abbreviated as “oz.”) is a unit of measurement for gauging the volume of many liquids.

It’s one of the most common measurements we use in everyday life, especially on food packaging, recipe measurements, and almost any other liquid-related application. 

Plus, when talking about ounces, we are typically describing either imperial (or “UK”) fluid ounces or US Customary fluid ounces.

In addition, make sure you know which type of ounce you need before measuring out any liquids!

Because both types of ounces are generally accepted globally and used interchangeably for all purposes, British citizens can use US Customary Ounces with no hassle — though it does mean that your measurements will be slightly off if you don’t pay attention to the type of ounce being used.

pouring milk

US ounce (fl oz) vs. Imperial fluid ounce

When converting Imperial measurements to US Customary measurements, there are very slight differences.

A single imperial fluid ounce (1 oz.) is equivalent to approximately 28.41 milliliters; while a US Customary fluid ounce (1 US fl oz.) contains 29.57 milliliters — 1 imperial fluid ounce is equal to 1.042 US Customary fluid ounces. 

The US ounce (oz) and the imperial ounce (oz) are both units of mass and volume.

However, the US ounce usually refers to a unit of liquid volume, while the imperial ounce usually refers to an Avoirdupois unit of mass.

One US liquid ounce equals 0.9607599 Imperial ounces, and one Imperial ounce is equal to 1.040842731 US ounces.

How many ounces in a gallon – depending on the US or UK

When measuring liquid volume, one US gallon (gal) equals 128 fluid ounces while one Imperial gallon equals 160 fluid ounces. 

This means that there are 128 fluid ounces in 1 US gallon and 160 fluid ounces in 1 Imperial gallon.

Therefore, when converting between gallons, be sure to note whether it is a US or Imperial gallon you are dealing with before beginning the calculation process.

To easily convert between gallons, ounces, and other units of measurement, consider using a calculator like the one we provided above or using the easy conversion chart below.

Doing so will save you time and hassle when trying to make quick conversions involving different measurement systems such as metric vs non-metric system measurements like liters and quarts or kilograms and pounds.

1.5 l to oz?

US customary fluid ounce

1 US fluid ounce = 1⁄128US gallon= 1⁄32US quart= 1⁄16US pint= 1⁄8US cup= 1⁄4US gill= 2US tablespoons= 6US teaspoons= 8US fluid drams= 1.804688 cubic inches= 29.5735 millilitres≈ 1.040843 imperial fluid ounces

US food labeling fluid ounce

Nutrition labels in America define a “common household” fluid ounce as exactly 30 milliliters.

30 milliliters ≈ 1.055852imperial fluid ounces≈ 1.014421US customary fluid ounces≈ 1.830712 cubic inches

Imperial fluid ounce

1 imperial fluid ounce = 1⁄160 imperial gallon= 1⁄40 imperial quart= 1⁄20 imperial pint= 1⁄10imperial cup= 1⁄5imperial gill= 8imperial fluid drams= 28.4131 milliliters≈ 1.733871 cubic inches≈ 0.960760US fluid ounces≈ the volume of 1 avoirdupois ounce of water.

What makes a gallon?

A gallon is a unit of measurement used in the English system of measurements, also known as the Imperial system.

The abbreviation for fluid ounce is ‘fl oz’ and you will often see a gallon referred to as a “gal”. In the United States, it is known as both the US liquid and US dry systems.

A gallon is made up of four quarts eight pints 16 cups or 128 fluid ounces (when using the US fluid measurement system).

One of the most common applications for this unit of measure happens when making recipes that call for a certain amount of liquid ingredients.

Flours and sugars are usually more accurately measured by weight, while liquids are usually measured by volume since they may vary in density.

tapioca flour substitute

When looking at how many ounces are in a gallon, it’s critical to note that these measurements don’t all necessarily equal one-thousandth of a liter (which is one milliliter).

It’s also wise to pay attention to which unit of measure you’re referring to; some countries use different increments than others.

For example, when talking about gallons of fuel consumption in automobiles, Imperial gallons will be used instead (4.54609 liters ≈ 1 Imp gal).

3 Types of Gallons

Sometimes, it’s confusing. Between a US gallon and an Imperial gallon, especially when you’re trying to figure out how many ounces are in a gallon.

To make it easier, here’s a quick look at the different sizes of gallons in the United States and the United Kingdom.

US Gallon

In imperial units and US customary units, the gallon is a unit of volume. Three different versions are currently in use: 

In the US and some Latin American and Caribbean countries, the US gallon (US gal) is defined as 3.785411784 L (231 cubic inches);

US dry gallon

US dry gallon (“usdrygal”) is one bushel of dry materials (exactly 4.40488377086 liters).

The US gallon is used throughout North America and is equal to 128 fluid ounces or 3.785 liters.

The US liquid gallon is divided into four quarts; each quart contains two pints; each pint has two cups; each cup holds 8 fluid ounces.

Imperial Gallon

In the United Kingdom, Ireland, Canada, Australia, New Zealand, and some Caribbean countries, the imperial gallon (IMP gal) is defined as 4.54609 liters.

The Imperial gallon (UK) is used in both Great Britain and Canada but is not commonly used in the United States.

It contains 160 fluid ounces or 4.546 liters, which makes it about 20% larger than a US liquid gallon! The Imperial liquid gallon is also divided into four quarts, but each quart has 2 pints that are slightly larger than their American counterparts.

Each imperial pint has 20 fluid ounces instead of 16 like the American pint does — making it 5% taller than the US version!

Therefore, if you are looking for how many ounces are in a standard type of “gallon” (regardless of type), then the answer would be 128 for US gallons and 160 for Imperial gallons!

From here we can see that the US liquid gallon is smaller. The following chart provides an easy conversion between different types of gallons:

how many ounces in a gallon of water

One-gallon gas can marked “U.S. Gallon” (for US users), imperial gallons, and liters (for Canadian users).

General information Unit of Volume Symbolgal Conversions 

1 IMP Gallon = 4.54609 Liters = 1.200950 US Gallon

1 US Gallon = 3.785411784 Liters = 0.8326742 IMP Gallon

How to convert ounces to gallons?

In the United States, gallons and ounces are two commonly used measurements of volume. The US customary system uses gallons to measure large volumes of liquid, while ounces measure smaller amounts.

To convert between the two measurements, it is helpful to be aware of the exact number of ounces in a gallon-sized container.

Here is an example of a quick reference chart:

1 Gallon = 128 Fluid Ounces

(4 quarts in a gallon) 1 Quart = 32 Fluid Ounces

(8 pints in a gallon) 1 Pint = 16 Fluid Ounces

(16 cups in a gallon) 1 Cup = 8 Fluid Ounces

Knowing how many fluid ounces are in a gallon can also be useful when calculating other basic measurements such as teaspoons and tablespoons. For example, one gallon is equivalent to 256 tablespoons or 768 teaspoons.

The weight is just over 10 pounds when measuring water at 39 degrees Fahrenheit. (If you don’t know how to convert temperature units, you can check this article: Celsius to Fahrenheit).

For more precise calculations, you may need to factor in things like temperature and density; substances usually have different masses depending on their temperature. 

If you want to ensure accuracy with any measurement conversion, consult additional reference materials that provide detailed information regarding various substances and their conversions under specific circumstances or conditions.

a gallon water to fl oz.

How to convert gallons to ounces?

Gallons and ounces measure different volumes, so they cannot be converted directly. Ounces are a smaller unit of measure than gallons, so you will need to use a conversion factor to convert from gallons to ounces.

To do this conversion, multiply the number of gallons by 128 (the number of ounces in 1 gallon).

For example, if you want to convert 2 gallons into ounces, you would multiply 2 X 128 = 256 ounces. You can use this method for all your volume conversions from gallons to ounces, or use the chart below for quick reference:

Gallons (gal) Ounces (oz)

1 gal = 128 oz

2 gal = 256 oz

3 gal = 384 oz

4 gal = 512 oz

5 gal = 640 oz

US fluid Ounces to Gallons Conversion Chart

Gallons (gal)US Fluid Ounces (fl. oz)
1 Gallon128 Fluid Ounces
1/2 Gallon64 Fluid Ounces
1/3 Gallon42 Fluid Ounces + 4 teaspoon
1/4 Gallon32 Fluid Ounces
1/8 Gallon16 Fluid Ounces
1/16 Gallon8 Fluid Ounces
1/32 Gallon4 Fluid Ounces
1/64 Gallon2 Fluid Ounces
1/128 Gallon1 Fluid Ounces
US fl. oz to US gal quick conversion chart

HOW MANY OUNCES IN A GALLON? – What we learned

A gallon is a unit of measurement for volume that is equal to 128 fluid ounces in the US. The international definition defines a gallon as equal to approximately 4.54 liters or 231 cubic inches. 

One US gallon is equal to 16 US cups, 8 pints, and 4 quarts. The capacity of a container will vary with its shape, so it’s easier to use reference charts and diagrams when measuring liquids in gallons.

You can use simple math equations or by using online calculators or conversion charts to convert between gallons and ounces (oz). For example, 2 gallons (gal) are equal to 256 ounces (oz).

To convert ounces to gallons, divide the number of ounces by 128; for example, 256 oz divided by 128 = 2 gal (2 gallons).

Knowing how many ounces in a gallon can help you accurately measure liquid ingredients for recipes and other household projects that require precise measurements.

With this knowledge at hand, you’ll have the tools you need to accurately calculate the amount of liquid necessary for any task with ease!

More Unit Conversions

how many oz in a gallon

How Many Ounces In A Gallon? (Calculator and Conversion Chart)

Have you tried to figure out how many ounces (fl oz) in a gallon? In this post, we will find out how many ounces are in a gallon with an easy conversion chart.
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Author: SHU-CHUN


  • 1 Gallon = 128 fl. oz US


  • To easily convert between gallons, ounces and other units of measurement, consider using a calculator like the one we provided above or using the easy conversion chart.

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