In our everyday lives, we come across many different measurements, like how many ounce units in a gallon? We use standard measurements like inches and pounds daily, and then there are metric unit conversions, which are used more often in scientific fields. Weighing systems differ in different regions of the world between the US Customary system measurement, the Metric system measurement, and the Imperial units system.
Learning about the different fluid ounce unit conversions can be tricky; it's important to know them to measure ingredients correctly when cooking or baking and to understand data presented in a scientific setting.
⬇️ Table of Contents
- Units of Measurement Systems | US Customary | Imperial | Metric
- What is a Gallon?
- What is a Fluid Ounce?
- How Many Ounces In A Gallon? - US/UK Measurements
- Ounce To Gallon Conversion Chart
- How Many Ounces In A Gallon Of Milk?
- Ounces To Gallon Volume Conversions
- Fraction Of Gallon To Ounces Conversion Chart
- Faqs

This blog post will review the conversion from fluid ounces to gallons and give you some handy conversion charts to reference.
Units of Measurement Systems | US Customary | Imperial | Metric
The Imperial system of unit measure was developed and used in the United Kingdom and its empire beginning in 1826. The Metric system measurement has, to varying degrees, replaced the imperial system in the countries that once used it. The US Customary system measurement was developed and used in the United States after the American Revolution, based on a subset of the English units used in the Thirteen Colonies; it is the predominant system of units in the United States.
What is a Gallon?
There are two types of gallons- the US gallon and the Imperial gallon.
The US gallon is derived from the volume of a cube with ten sides, each measuring 1 inch. It is equivalent to exactly 231 cubic inches, or 3.785 liters.
The Imperial gallon was originally defined as the volume of a cylinder with a base radius of 1 foot and height of 1 foot. It is equivalent to exactly 4 Imperial quarts, or about 4.55 liters.
Due to its non-standard nature, it is no longer used in day-to-day life in the United Kingdom, but some legacy units of measurement still exist. For example, there are precisely 20 Imperial gallons in a British barrel.
What is a Fluid Ounce?
An ounce is a unit of measurement typically used to measure weight. There are 16 ounces in a pound and 28.35 grams in an ounce. In the United States system, there are 128 ounces in a gallon. In the Imperial system, there are 160 ounces in a gallon.
How Many Ounces In A Gallon? - US/UK Measurements
In one gallon using the US Customary system liquid measurements, there are 128 fluid ounces in one liquid gallon. The UK Imperial measurement for 1 gallon contains 160 fl oz, much more than the US Customary system.
Ounce To Gallon Conversion Chart
- 1 US Gallon in Ounces = 128 fl oz
- 1 Imperial Gallon in Ounces = 160 fl oz
Number of Fluid Ounces | US Customary System Percentage of 1 Gallon | UK Imperial System Percentage of 1 Gallon |
---|---|---|
1 oz | 00.78125% | 00.625% |
2 oz | 01.5625% | 01.25% |
3 oz | 02.34375% | 01.875% |
4 oz | 03.125% | 02.5% |
5 oz | 03.90625% | 03.125% |
6 oz | 04.6875% | 03.75% |
7 oz | 05.46875% | 04.375% |
8 oz | 06.25% | .05% |
9 oz | 07.03125% | 05.625% |
10 oz | 07.8125% | 06.25% |
20 oz | 15.625% | 12.5% |
30 oz | 23.4375% | 18.75% |
40 oz | 31.25% | 25% |
50 oz | 39.0625% | 31.25% |
60 oz | 46.875% | 37.5% |
70 oz | 54.6875% | 43.75% |
80 oz | 62.5% | 50% |
90 oz | 70.3125% | 56.25% |
100 oz | 78.125% | 62.5% |
110 oz | 85.9375% | 68.75% |
120 oz | 93.75% | 75% |
128 oz | 100% | 80% |
130 oz | 81.25% | |
140 oz | 87.5% | |
150 oz | 93.75% | |
160 oz | 100% |
UK Imperial System for 1 Gallon to oz
- 1 Imperial Gallon = 1.2009499 fl oz
- 1 Imperial Gallon Conversion =133.2279 fl oz
1 Gallon of Water to Pound/Kg Conversion
- Density = 0.998 kg/l
- Weight (lb) = 8.329 lb
Here's a link for a conversion amount calculator
An Ounce is a unit of weight, and a gallon is a unit of volume. To convert between them, you need to know the density.
How Many Ounces In A Gallon Of Milk?
A gallon of milk typically weighs 8.6 pounds, which works out to around 128 ounce units. However, because milk is a liquid, its weight can vary slightly depending on its density. This is because milk is generally around 8% milkfat, and one gallon of milk weighs about 8.6 pounds.
So, for every pound (16 ounces) of milk, there would be about 0.8 fluid ounces of milk fat. This means approximately 103 liquid ounces of milk (not including the milkfat) in a gallon and 128 ounces when including the fat.
Milk Gallon to Pound Conversion
- Density = 1.035 kg/l
- Weight (lb) =8.637 lb
Ounces To Gallon Volume Conversions
Measurements | Number Of Units |
---|---|
Tablespoons | 256 |
Teaspoons | 768 |
Quarts | 4 |
Pints | 8 |
Cups (US) | 16 |
Cups (Imperial) | 13.32275 |
Liter/Litre | 3.78540118 |
Milliliters | 3785.40118 |
Fraction Of Gallon To Ounces Conversion Chart
There are 128 ounces in a gallon. A half-gallon is 64 ounces. 160 Imperial fluid ounces in a gallon in the Imperial system and 80 Imperial fluid ounces in a half gallon.
Faction Measurements | Ounces |
---|---|
1 Gallon | 128 oz |
¾ of a Gallon | 96 oz |
⅔ of a Gallon | 84.48 oz |
½ of a Gallon | 64 oz |
⅜ of a Gallon | 48 oz |
¼ of a Gallon | 32 oz |
⅓ of a Gallon | 42.24 oz |
⅛ of a Gallon | 16 oz |
Faqs
How Many Glasses of Water In One Gallon
The old saying is to drink 8 eight-ounce glasses of water a day. This comes from the outdated understanding of drinking a whole gallon a day.
How Many Cups in a Gallon?
There are 16 cups in a gallon in the United States measurement system. The Imperial measurement system has slightly different measurements, with about 13.3 cups making up a gallon.
So depending on which system you're using, the answer will be slightly different.
Should I Drink 8 Eight-Ounce Glasses of Water a Day?
Yes! The health benefits of drinking the correct amount of water for your body weight are numerous. For example, drinking enough water helps to flush toxins out of your system, keeps your skin healthy, and can even help you lose weight.
To determine how much water you should drink each day, divide your body weight in half and drink that many ounces of water per day. So, if you weigh 150 pounds, you would drink 75 ounces of water daily.
If you have difficulty drinking enough water throughout the day, try carrying a refillable water bottle with you to always have access to fluids.
How Many 32 oz Bottles Make a Gallon?
There are 4 quarts in a gallon, so 4 x 32 oz bottles equal = 128 ounces. Therefore, four water bottles make a gallon.
How Many 16 oz Bottles Make a Gallon?
16-ounce water bottles would fit into a gallon 8 times. This means you would need eight 16-ounce water bottles to make a gallon.
How Many 8 oz Bottles Make a Gallon?
There are 8 eight-ounce bottles in a gallon.
Tips For Drinking Enough Daily Water Intake
We all know we should drink plenty of water daily, but sometimes it's hard to ensure we're getting enough. Drinking enough water to stay hydrated is important, but drinking too much water can be harmful.
A great post covering the good and the bad of drinking water, HealthLine
If you're looking to increase your water intake, here are a few tips that can help:
1. Make it convenient. Invest in a good water bottle you can take wherever you go. That way, you'll always have water on hand when you get thirsty.
2. Drink first thing in the morning. Start your day by drinking a big glass of water as soon as you wake up. This will help hydrate your body from the night's sleep and set the tone for the rest of the day. Consider drinking Lemon Water In The Morning for the best health effects.
3. Set reminders throughout the day.
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Ounces In A Liter 💧 US Customary, Metric & UK Imperial
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