Different Unit, Same Length

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SWBAT measure the same object using different nonstandard units.

Big Idea

This lesson doubles as an extension in first grade and as an introduction to 2nd grade measurement. Students notice how different units affect their measurements.

Setting Up the Learning

5 minutes

This lesson allows for students to practice measuring with nonstandard units, and also prepares them for the standard they will see in 2nd grade related to this. It could also work as an introduction for 2nd grade teachers. (CCSS.Math.Content.2.MD.A.2 Measure the length of an object twice, using length units of different lengths for the two measurements; describe how the two measurements relate to the size of the unit chosen.) 


We have been measuring for a few days, but each day we have only used 1 unit. In real life, people who measure objects have to choose which unit would be best for them to use.


We measure all the time in real life. When your mom sees if you have a fever, she is measuring how hot or cold you are. When you check the clock, you are measuring how many minutes something takes. Fishermen have to measure fish to determine if they are a keeper or not. When we measure how long something is, we are measuring length

Objective :

Your thinking job today is: What happens when we measure the same object with different units? 

Opening Discussion

15 minutes

Present problem: Yesterday we measured our classroom carpet using cubes. That took forever and a lot of cubes! How could we measure the rug faster?

I have 3 units available for students to discuss and think about: large paperclips, pencils, notebooks

Partner Talk: Which unit should we use so we can measure the rug faster? (I want to see how students are initially thinking) 

I’ll have students vote on which one they think will make us faster.

Partner talk: Try to convince your partner that you are right!

  • CCSS pushes students to articulate arguments (MP3) - I’ll choose one argument for each unit to share with students.


We will measure the rug using each unit. We will time how long it takes to measure each one. I use onlinestopwatch.com on the promethean board!

After we measure the rug using all of the units and record the times for each measurement experience and how many units, we will discuss why it worked that way.

Guiding Questions:

  • Which unit took the longest? How many paperclips did we need? We needed a LOT of paperclips.
  • Which unit was the fastest? How many journals did we need?
  • Why did we only need ___ journals, but we needed so many more paperclips. Why are the numbers different? 

Revisit the original problem: Which unit can we use to make measuring the rug faster? 

Student Share

10 minutes

After we measure the rug in both units, students discuss in partners/small groups WHY the measurements were different.

See attached Different Units video for student discussion on the rug! This is a great example of a way to incorporate Speaking and Listening standards in math!

After they discuss in small groups, we will share out as a class things that I heard. Then we will see if we can apply what we are predicting to other situations.

  • For example, "If I measured the rug in cubes and in crayons, would I need more cubes or more crayons? How do you know?"

Independent Practice

15 minutes

Students create an "I Can Measure" booklet (see attached).

In the booklet, they measure a picture of an object using 2 units. Then they measure the actual object using both units. At the end of the booklet, there is an extension question, which asks students why the number of units changes when you change the unit. (This is aligned to the CCSS mission to have writing across the curriculum!)

See attached pictures for examples of student responses to this question:

See attached Independent Practice Discussion video for a discussion with a child about his measurements! He's a cutie.


5 minutes

We will close the lesson by coming back to the carpet and sharing our answers to the last question in the booklet. Students will read their answers to each other and then I will share out a few exemplar responses.