# How to teach measurement comparisons with length in three easy steps

Updated: Dec 23, 2021

Do you find it difficult to break down the concept of measurement when teaching kindergarten math?

There are two major concepts of measurement to explain to children.

Measuring against an object (e.g. how many blocks long is this pencil?) and measurement by comparison (e.g. which is the longest or shortest?).

This lesson introduces the concept of measurement as it relates to** comparison between objects** and will help you teach children that common objects can be used as a tool to measurement by comparison (e.g. pieces of wool or hands).

As with any lesson on a new topic, you must first start with exploring the language required.

**1. VOCABULARY**

What does ‘length’ mean?

Brainstorm what students know before going any further and have a short class discussion about how the term is used in everyday life ‘Look at the length of this pencil’.

The simple rules I follow are:

· Vocabulary understanding

· Identifying

· Comparing

Once the vocabulary has been taught, you can reinforce these terms throughout the lesson by using them purposefully. This can be through saying the terms with emphasis and pointing to the word on the wall again and again.

**2. IDENTIFYING**

How can we identify what the length of an object is? (Usually the longest side) Ask a student to show me the length of the whiteboard with their finger. Ask another student to show me the length of their arm with their finger.

**3. COMPARING**

Pull out a bag of different lengths of wool (or paper). I use a large set to demonstrate this on the board first and then give students a bag per table of wool of differing lengths to share out.

How can we find the longest piece of wool?

*By putting each piece side by side, matching ends.*

Can they be wobbly, or do they need to be straight?

*Straight with one end touching at the same point.*

[Depending on your particular state curriculum, I would not introduce the term ‘width’ yet until students are confident with basic measurement terms]

Place all of the pieces of wool with Bluetak on the whiteboard and be sure to mix up the order of the lengths and see if students start intuitively reacting that they should be in length order.

Then ask students if we can arrange the pieces of wool in order by length.

Ask a student to come to the whiteboard and find the longest piece of wool and then move this to one end of the whiteboard.

Then ask more students to come to the whiteboard and move a piece of wool to the correct position on the board by length. Be sure to stick to the terms long/longest/length and keep these written on the board so you’re reinforcing that vocabulary all the time.

Make sure you explain to students that the length of the object is the same no matter how the pieces are arranged on the whiteboard.

Once all the pieces are arranged in length order, then introduce the terms short and shortest by showing the difference.

To keep students engaged, send them to the tables and let them take 5 pieces of wool from a bag of mixed wool lengths and arrange these from the longest to the shortest on their paper and stick them down. This is a great quick formative assessment tool to check for understanding.

Once this has been done, students can return to the floor and you can have a short discussion about how to use the wool to measure the length of objects around the classroom. Demonstrate by holding a piece of wool against the longest part of the table.

Give each child a piece of wool (of different lengths) and ask them to find two things in the room that are the SAME length as each other by holding the wool length against it. Students will have lots of fun trying to find two things that are the same length and this is where I would be making observations to see who truly understands the concept of a piece wool as a measurement tool.

When complete, return children to the floor and ask them what problems they had measuring.

You can finish the activity by getting students to play with playdough and make long and short objects on their mats.

Other ideas for measuring length can be to get students to use their hands as measurement tools. Draw around their hand, cut it out and then use it as a non-standard unit of measurement to measure the length of objects in the classroom.

Note: you can introduce the terms short, shortest, shorter, tall, taller, the same length as, as long as, as short as, compare, beside and next to as necessary as the lesson progresses.

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