# What is Capacity?

A thorough explanation of how to measure capacity using both the metric and customary systems of measurement, with helpful conversion charts and practice questions

Author
Tess Loucka

Published
November 7, 2023

# What is Capacity?

A thorough explanation of how to measure capacity using both the metric and customary systems of measurement, with helpful conversion charts and practice questions

Author
Tess Loucka

Published
Nov 1, 2023

# What is Capacity?

A thorough explanation of how to measure capacity using both the metric and customary systems of measurement, with helpful conversion charts and practice questions

Author
Tess Loucka

Published
Nov 7, 2023

Key takeaways

• The most used system of capacity measurement in the world is the metric system. Only 3 countries use the customary system: the United States, Liberia, and Myanmar.
• The metric system is centered around the liter. To measure larger or smaller amounts of something, multiples or fractions of the liter are used.
• The customary system uses a wide range of units to measure capacity. These units are teaspoons, tablespoons, ounces, cups, pints, quarts, and gallons.

When a recipe calls for an ounce of milk, 2 cups of flour, 1 cup of sugar, or 1 teaspoon of baking soda, these measurements all refer to a very particular amount of something.

Every container, whether it be a cup, a bathtub, or a barrel, can only hold a particular amount of liquid before it fills up, and this idea is referred to in science as capacity.

A glass can only be filled up so high with orange juice before it spills over. Similarly, a cereal bowl can only hold so much milk until it reaches the brim and drips down the sides.

When you take a bath and fill the tub with water, go to water your plants and fill up your watering can, or fill up a water gun when you’re at the beach, you’re really thinking about capacity!

Capacity is a measurement that can be used to better understand countless areas of your daily life and the world around you, but what is capacity and how do we measure it?

## What is capacity in math?

Here’s a simple definition of capacity: capacity refers to the amount of something that an object can hold before spilling over. Another capacity definition is the maximum amount of something—whether that be a solid, liquid, or gas—that fits into a given container.

There are two systems of measurement commonly used for measuring capacity—the metric system and the customary system.

Both systems are frequently used around the world, so understanding how both of them work will come in handy!

## Metric vs Customary Unit of Capacity

The metric and customary systems of measurement are the most popular systems used around the world for measuring capacity. While they both are used to measure the same thing, the units they use are very different.

In the United States, the customary system is used. Only two other countries in the world use the customary system—Liberia and Myanmar. Why only these three countries?

Well, the US had already been using the customary system of measurement, or the precursor to it, before the metric system was created. Factories in the US used the customary system and by the time American politicians had the opportunity to switch the country to the metric system, they believed it would be too much trouble and would cost the US too much time and money.

Liberia was a US colony and continues to use the same measurement system as the US. Myanmar’s isolation prevented them from adopting the metric system until very recently. Today, Myanmar is one of the few countries that actually uses both customary and metric units.

All other countries use the metric system!

### Metric vs Customary Unit of Capacity

The metric system uses the units of liters (l), milliliters (ml), and other related units.

One liter is equivalent to 1,000 milliliters. We can write that out as:

1 l = 1000 ml

Knowing that fact then allows us to gather a few more measurements:

½ l = 500 ml

¼ l = 250 ml

⅕ l = 200 ml

and so on…

Besides liters and milliliters, there are a few other units of measurement used in the metric system. They can be seen in the following chart:

Kiloliter =/1,000
Hectoliter =/100
Decaliter =/10
Liter
Deciliter =x10
Centiliter =x100
Milliliter =x1000

A unit of capacity to the left is larger than a liter. A unit of capacity to the right is smaller. To convert 1 liter to hectoliters, simply divide 1 by 100 to get 0.01 hectoliters. To convert 1 liter to milliliters, just multiply 1 by 1,000 to get 1,000 milliliters.

One way to remember the units of the metric system is to remember that “King Henry Died Unusually Drinking Chocolate Milk.” In this case, the U stands for unit of capacity, or liter!

### Customary Units of Capacity

Customary units for measuring capacity include teaspoons, tablespoons, ounces, cups, pints, quarts, and gallons.

1 teaspoon = 3 tablespoons

1 ounce = 2 tablespoons

1 cup = 8 ounces

1 pint = 2 cups

1 quart = 2 pints

1 gallon = 4 quarts

## Measuring Capacity

Measuring capacity often requires you to have a tool called a graduated cylinder. These are cylindrical containers with marks on the side that measure its capacity.

If you have a container with an unknown capacity, you can fill the container with water, then pour that water into a graduated cylinder. The line on the cylinder at which the surface of the liquid is touching is the container’s capacity.

Measuring capacity can also be done by simple math and unit conversion. Let’s say you have a container with an unknown capacity. You can take a known amount of water, such as a cup, and fill the container up until it is full, taking note of exactly how many cups of water you poured in.

If 10 cups and 3 ounces of water filled the container, then you know that the container has a capacity of 10 cups, 3 ounces.

Estimating a container’s capacity can also come in handy and can be done easily with a firm understanding of the units of capacity measurement.

To put things into perspective,

A swimming pool may have about 1,800 kiloliters or 490,000 gallons of water.

A bathtub, on average, holds about 302 liters or 80 gallons.

A typical bottle of water may hold 0.5 liters of water or 16.9 ounces.

A tube of toothpaste might hold 75 ml or 2.5 ounces of toothpaste.

So, if you take a look at a bowl of cereal and want to estimate its capacity, what unit will you use?

Kiloliters, liters, or milliliters?

And what about gallons, cups, or ounces?

Well, cups might be the best unit in this case.

Understanding how units of capacity measurement work gives you a deeper understanding of the world around you. For more practice with capacity, look for a math app or website with resources such as conversion charts and practice problems that will support you as you learn.

## Practice problems for measuring capacity

Click on the boxes below to see the answers!

What is the capacity definition?

In the United States, we use customary units. The customary units are teaspoons, tablespoons, cups, ounces, pints, quarts, and gallons.

Metric units of capacity are all related to the liter. The units are kiloliters, hectoliters, decaliters, liters, deciliters, centiliters, and milliliters.

The standard unit of capacity in science is the liter.

Lesson credits

Tess Loucka

Tess Loucka discovered her passion for writing in high school and has not stopped writing since. Combined with her love of numbers, she became a math and English tutor, focusing on middle- and high-school-level topics. Since graduating from Hunter College, her goal has been to use her writing to spread knowledge and the joy of learning to readers of all ages.

Tess Loucka

Tess Loucka discovered her passion for writing in high school and has not stopped writing since. Combined with her love of numbers, she became a math and English tutor, focusing on middle- and high-school-level topics. Since graduating from Hunter College, her goal has been to use her writing to spread knowledge and the joy of learning to readers of all ages.

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