How Many Ounces in a Gallon of Water? Explained

Ounces(oz) is a measuring unit for weight and volume, converted into other units such as grams, pounds, or gallons. A gallon(gal) is also a unit of volume. We need to know how to convert ounces into gallons and vice versa. The article will help you understand these common conversions.

How Many Ounces in a Gallon?

There are 128 ounces in a gallon. Concerning the metric system, 160 fluid ounces equals 1 gallon of water.

What is a Gallon?

A gallon is a unit of volume by the Imperial units and the United States customary units. Currently, there are three different versions of a gallon.

  • Imperial Gallon (imp gal): Imperial gallon equals 4.54609-liter. Previously, it was used in the United Kingdom, Australia, Canada, Ireland, and some Caribbean countries.
  • US Gallon (U.S. gal): It is 231 cubic inches, which equals exactly 3.785411784 liters. It is currently used in the United States and Caribbean countries.
  • U.S. Dry Gallon (“usdrygal” ): It is defined as 1⁄8 US bushel, which is exactly 4.40488377086 liters. 

As stated in the IEEE standards, the symbol for imperial and U.S. gallon is a gal

A gallon contains four quarts and eight pints, with different volumes in different systems. There are 128 ounces per gallon.

What is an Ounce?

An ounce is one of the units of measurement for different quantities like mass, weight, and volume. It was derived from an ancient Roman unit of measurement named uncia. According to the United States customary and British Imperial units, the avoirdupois ounce equals 1⁄16 avoirdupois pounds, exactly 28.349523125 grams. 

Ounce was mainly used in the United States to measure canned foods, postal packages, the areal density of paper and fabric, and many more.

The term ounce has different versions, including:

  • Troy ounce: It is exactly equal to 31.1034768 g. Troy ounce is used to measure the mass of rare-earth metals such as gold, platinum, palladium silver, rhodium, etc.
  • Ounce-force: It is defined as the 1⁄16 of a pound-force equals 0.2780139 newtons.
  • Fluid ounce: It’s a measure of volume. A fluid ounce equals 29.6 ml in the U.S. system and 28.4 ml in the Imperial language of measurement. 
  • Dry Ounce

How many water Bottles are there in a Gallon?

In the United States, the water bottles are usually 8oz, 12oz, 16.9oz, 20oz, and 24oz in sizes. Whereas in the U.S. measurement system, 1 gallon equals 128 fluid ounces. Therefore, we divide 128 by the water bottle size to measure how many water bottles are in a gallon. For example, we need to know how many 16.9oz water bottles are in U.S. gallons. Just divide 128 by 16.9; we’ll get 7.57 water bottles upon simplification.

Contrastly, in the United Kingdom, 1 gallon is equal to 160 fluid ounces. Therefore, we divide 160 by the size of the water bottle to measure how many water bottles are there in a fluid gallon. For example, we need to know how many 16.9oz water bottles are there in the U.K. gallon. Just divide 160 by 16.9; we’ll get 9.47 water bottles upon simplification.

How to convert Gallons to Ounces?

The gallons to ounce conversion is as follows:

  • Concerning the U.S. measurement system, 1 gallon = 128oz. We need to multiply the number of gallons by the number of ounces present in one gallon for gallon – ounce conversion. For instance, we want to know how many fluid ounces are there in 3 liquid gallons. Multiply 3 with 128 to get the desired result which equals 384 ounces.
  • For the U.K. measurement system, 1 gallon = 160oz. We need to multiply the number of gallons by the number of ounces present in one gallon for gallon – ounce conversion. For instance, we want to know how many fluid ounces are there in 3 liquid gallons. Multiply 3 with 160 to get the desired result which equals 480 ounces.

How many ounces makes a half a Gallon?

We need to know how many ounces make a half gallon. Simply multiply the total ounces present in one gallon by ½ to obtain the desired result. 

Concerning the U.S. measurement system, 1 gallon = 128oz. The conversion ratio shows that there are 64 fluid ounces in ½ gallon. 

For the U.K. measurement system, 1 gallon = 160oz. The conversion ratio shows that there are 80 fluid ounces in ½ gallon.

How Many Ounces of Water Should I Drink a Day?

How Many Ounces of Water Should I Drink a Day?

There are different viewpoints on how much water is enough for a healthy day. Dietitians and nutritionists recommend that you need to drink 64 ounces of water daily to prevent dehydration because our body continuously loses water through sweat or urine. In other words, you should take eight 8-ounce (known as 8×8 rule) glasses daily, which equals half a gallon. 

Water balance is necessary for the health and proper functioning of your body. Although staying hydrated is crucial, hydration needs are highly individual. How much water you need may depend on the following factors:

Where you live

You’ll need more water if you live in hot and humid areas. The same is the case with people living in the mountains or at a high altitude.

Your diet

Water consumption also depends on your diet plan. You’ll need more water if you drink a lot of coffee or caffeinated beverages. The same is the case with people who like to eat salty, spicy, and sugary foods. 

Seasons and temperature

Your water demands will increase in hot seasons because of perspiration.

Your environment

You may feel thirsty if you spend more time in a heated room or the sun.

How active you are

If you have been active throughout the day, you need to drink more water.

Your health conditions

You should drink more water to stay hydrated if you feel sick or your body loses fluid through vomiting or diarrhea. You should read about How long does it take to pee after drinking water.

How many ounces in a Cup and How many Cups in a Gallon?

Measuring Cups for Liquid: One standard cup can contain 8 liquid ounces. It equals 1/2 pint or 237 mL. These plastic or glass cups are usually marked with a measurement line. The line helps in the liquid measurements. Cooking experts also use measuring instruments along with these measuring cups. 

Measuring Cups for Dry Ingredients: Customarily, one dry cup equals 6.8 U.S. dry ounces. You can exactly measure 16 tablespoons, 0.5 pounds, or 221.23 grams of dry ingredients using a dry cup. As you know, dry materials may have the same volume as the fluid, but they do have different weights. Consequently, don’t forget to level the measuring cup with a butter knife for precise mass measurements. 

Another question is how many cups are contained within one gallon. Considering the U.S. standards, one gallon of water equals 16 cups.  

FAQ – How Many Ounces in a Gallon of Water

How many ounces are in a gallon and a half


There are 128 ounces in a full gallon and 64 ounces in a half gallon.

How many ounces are in a quart in Canada


The Imperial or Canadian quart is almost 20 percent bigger than the U.S. quart. Therefore, the U.S. quart is equal to 32 ounces; however, the Canadian quart is equal to 40 ounces.

How many gallons are in a 2.0 liter Bottle of Soda


We need a gallon to liter conversion to know how many gallons are in a 2-liter bottle of soda. 

As we know, 1 gallon = 128 oz

2.0 liters = 2(33.824)oz = 67.628 oz (Less than a gallon)

As 2-liter soda bottle contains 67.628oz fluid, divide the answer by 128 to convert it into gallons: 67.628/128 = .5284 or 52.84 %

Therefore, 2 liters is 52.84% of a gallon or 2.0 L = 0.5284 gal.

How many ounces are in a U.S. gallon


A U.S. gallon contains 128 ounces of fluid.

How many 32 oz make a gallon?


Customary measurements suggest that we need 4 32oz to make a liquid gallon because 1 gallon equals 128oz according to the U.S. measurement system.

How many Gallons does 64 Ounces equal?


For the U.S. measurement system, 1 gallon = 128oz. The conversion ratio shows that 64 ounces equal ½ gallon. 

Is 1 gallon the same as 64 oz?


No, 64 ounces do not make a gallon. According to the U.S. measurement system, 1 gallon = 128oz. Therefore, we can say that 1 gallon is the same as 128oz. In other words, 64oz equals ½ gallon.

Final Words – How Many Ounces in a Gallon of Water

Ounces(oz) is a measuring unit for weight and volume, converted into other units such as grams, pounds, or gallons. We need to understand the relation between gallons and ounces for common kitchen conversions. 

There are 128 ounces in a full gallon and 64 ounces in a half gallon. One gallon equals 4 quarts, 8 pints, 16 cups, and 3.8 liters. Here you can read full guid about how long does it take for water to freeze or how long does it take for water to boil?

Leave a Reply

Your email address will not be published. Required fields are marked *