Length Lesson for Kids: Definition & Measurement

Instructor: Bethany Calderwood

Bethany has taught special education in grades PK-5 and has a master's degree in special education.

Both in math class and in real life, you'll work with many different types of measurement. In this lesson, you'll learn the definition of length, while practicing how to measure it using both standard and nonstandard units.

What Is Length?

The length of an object is its most extended dimension - that is, its longest side. The length of your dog, for example, would be from the tip of its nose to the end of its tail. That distance is greater than the distance from the top of its head to the bottom of its feet. The length of your giraffe, on the other hand, would be from the top of its head to the bottom of its feet, because that distance is greater than the distance from the tip of its nose to the end of its tail. Look at the picture. The red lines show the lengths of the two animals.

length of giraffe and dog

Measuring Length in Nonstandard Units

Bev wants to measure the length of the hallway outside of her classroom. She notices that the floor is made up of square tiles, so she decides to measure by counting the tiles. Bev finds that from one end of the hallway to the other there are 249 tiles. The length of the hallway is 249 tiles.

Next, Bev decides to measure her lunchbox. The lunchbox doesn't have tiles, so she decides to line up milk cartons. The length of Bev's lunchbox is 4 milk cartons. Bev's friend Jim's lunchbox is 5 milk cartons long.

Both the tiles and the milk cartons are called nonstandard units. Nonstandard units can be used to measure length and make comparisons, but they have limited meaning. Since not all tiles are the same length, it would be hard for Bev to share her measurement with someone who could not see her school's hallway. The same is true of the milk cartons.

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