Fluid Ounces: Definition, Conversion,and Solved Examples
reviewed by Jo-ann Caballes
Updated on October 15, 2024
Welcome to Brighterly, where you’ll find learning math easy, fun and engaging!
Today, we’re going to delve into a key measurement you’ll encounter in everyday life: the fluid ounce.
The fluid ounce can be easily converted to many other units of measurement, including pints, cups and even dry ounces.
Here, we’ll cover the definition of a fluid ounce, how to measure US fluid ounces and how they compare to ounces. We’ll also give you the tools to practice and hone your knowledge with our practice questions and free math worksheets.
What is a fluid ounce?
A fluid ounce is a unit of measurement. As you’ve probably guessed from the name, the fluid ounce specifically measures liquid and fluid substances, not solid ones. It is part of the imperial system of measurement and measures the capacity or volume of liquid substances. The fluid ounces abbreviation is fl oz, which is often how you’ll see it presented in math problems.
How to measure fluid ounces
You can use a number of different tools specifically designed to measure fluid ounces. These tools measure volume rather than weight, so you won’t need a pair of scales for this exercise.
The tools you can use to measure US fluid ounces include:
- Measuring jugs
- Baby bottles
- Cups (one cup measures 8 fluid ounces)
- A syringe
- A shot glass
What does 1 fl oz look like?
1 fl oz is a relatively small measurement. One fluid ounce is equal to around 30 ml. As some 1 fluid ounce examples, this is the standard measurement for a full medicine cup. A travel-sized tube of toothpaste or a small bottle of facial serum usually measure around 1 US fl oz too.
How much is an ounce of water?
We measure water in fluid ounces because it is a liquid. One fluid ounce is equal to:
- 29.5735295625 ml
- 2 tablespoons
- 1/16 pint
- 1/32 quart
- 1/128 gallon
How much does 1 fluid ounce weigh?
1 fluid ounce will weigh roughly 1 ounce, or 28.35 grams. That’s because, while the fluid ounce and ounce measure units in different ways, their weights are similar. However, the density of the liquid also plays a factor – dense liquids will weigh more, while thinner liquids will weigh less
Ounces vs fluid ounces: difference
The key difference between ounces and fluid ounces are what they weigh and how they measure their units. Ounces are used as standard to measure dry or solid items, and they are a unit of weight measurement. This means they weigh how heavy an item is.
US fluid ounces are usually used to measure liquids. They measure the volume of the liquid, or the capacity of a container. However, ounces can also measure the weight of liquids – but as standard, we measure liquids by volume.
Fluid ounces to ounces
There are a couple of steps to take to convert fluid ounces to weight ounces – it’s not as simple as measuring your liquid’s volume then measuring its weight.
The density of a liquid affects how much it’ll weigh. First, you need to work out the density of your item using the formula density = mass ÷ volume.
Then, you’ll use this formula to calculate your fluid ounces to ounces: ounces = fluid ounces × 1.0432 × density.
You can reverse this sum to convert ounces to fluid ounces, aka oz to fl oz conversion.
Fluid ounces conversion
US fluid ounces can be converted into many different units of measurement:
- US fluid ounces to millimeters: fluid ounce x 29.574
- US fluid ounces to ounces: fluid ounce × 1.0432 × density
- US fluid ounces to pints: fluid ounce x 16
- US fluid ounces to gallons: fluid ounce x 128
Solved math tasks: examples
Fluid ounces are a key unit of measurement that you’ll not only encounter in math, but also your everyday life. Now that you’ve learnt the essential info, try out our solved math problems below – once you’ve finished, check the answers and see how many you got right.
Solved math task 1
You have a bottle of water that contains 20 US fluid ounces. How many cups would you be able to get out of this bottle of water?
Answer:
| 2.5 cups. |
1 oz of water weight is ⅛ of a cup. In other words, there are 8 fluid ounces to a cup. Therefore, you need to divide your number of fluid ounces by 8 to get your answer.
20 fl oz ÷ 8 = 2.5 cups.
Solved math task 2
You have a recipe that requires 4 quarts of milk. How many fluid ounces is this equivalent to?
Answer:
| 128 fl oz. |
There are 32 fluid ounces in every quart, so to get your number of fluid ounces, you’ll need to multiply your number of quarts by 32.
4 quarts x 32 = 128 fluid ounces. That’s how many fluid ounces are in 4 quarts.
Solved math task 3
You need to convert 5 US fluid ounces of water into ounces, and your ingredient has a density of 0.7 g/ml. How much is this water weight per oz?
Answer:
| 3.6511 oz. |
To calculate fluid ounces with density, you need to multiply those numbers by 1.0432.
5 fl oz × 1.0432 × 0.7 g/mL = 3.6511 oz
Fluid ounce: practice math problems
Fluid ounce: worksheets
Practice makes perfect, so hone your newfound knowledge on US fluid ounces and units of volume and measurement with our cool free math worksheets!
- Measuring liquid volume worksheets
- Measuring units worksheets
- Volume worksheets
- Surface area and volume worksheets
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