How To convert Ounces to Pounds

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Students will use customary units of length to convert ounces to pounds.

Big Idea

Students will be able to apply foundational understanding to help them assist with converting ounces to pounds on their own.

Warm Up Section

20 minutes

To begin this lesson I want to build on to what my students already know. In third grade students learned what ounces and pounds generally measure. To be sure I ask students to tell me what can we measure by pounds and ounces.  Students could readily determine what ounces and pounds are used to measure. Since, we have covered how to convert feet to yards, I will begin this lesson discussing the U.S. Customary System.

 Customary System

1 lb = 16 oz

 I want students to gain understanding to help assist them with measure concepts.  It is my goal to help them understand that larger units can be subdivided into equivalent unit,  the same unit can be repeated to determine measure, and that the relationship between the size of a unit and the number of units needed. Example 1 pound = 16 ounces.

In the instructional portion of a lesson, I would provide more examples. But here, at the start, I'm probing. I want to see how many of my students can use what we have been learned about conversion to determine how to convert ounces to pounds. This is important because I would not want to teach a lesson when the required skills have not been met. 

So, if I give you guys 32 ounces how many pounds would that be?  How do you know?  What skills did you use to determine the amount of pounds?  What if I give you 48 ounces, how many pounds would that be?  

After students respond, I ask how would you prove that? 

Students need to demonstrate their knowledge of how to convert among different size of standard measurement units within a given measurement system. By the end of this lesson students should be able to apply the given foundation to solve multi-step problems own their own.

 This lesson will be focusing on the following Mathematical Practices:

MP.2. Reason abstractly and quantitatively.

MP.5. Use appropriate tools strategically.

MP.6. Attend to precision

MP.8. Repeated Patterns

Working Together

20 minutes

Material: conversion chart.docx

 Before they begin solving the given problems, I ask students to recall what they learned about converting feet to yards in a previous lesson.  Can anyone think of a way to apply those same problem solving skills to convert ounces to pounds?  Some student makes the connection. 

Because some students are still struggling, I say to them when you want to know how much something weighs, you can measure it in pounds and ounces.  I ask students what tool can you use to measure something in pounds? (scale) What about ounces?  Students were unable to respond, so I ask how many of you have a baby sister.

( student: I do  Teacher: How much did she weigh?  Student: 16 pounds and 3 ounces.  Teacher: Are you sure about that?  Student: I mean 6 pounds and 3 ounces.)  

Even though  the student seems a little unclear about the weight, she still had some knowledge about ounces.  Most of my students have some prior knowledge of ounces and pounds.

Moving Forward:

Are you guys ready to learn how to convert? Some students need to see how to work through each step.  So, I will model how to convert ounces to pounds.  I think about what my students already know and what they need to know in order to convert successfully.  Then, I tell them the best way to become familiar with new units of measurement is to explore the patterns and relationship during conversion.

I draw a customary conversion table on the board. How many ounces do we need to make a pound? 16 Ok!  What if I had 2 pounds, how many ounces would it take? 32 Think about your answer.  What happened to the ounces when I increased the pounds? It increased by 16 (16 X 2). Then I will continue to increase the pounds to see if students can use their knowledge of relationship between units and their understanding of multiplicative situation to make the next 3 conversion on their own.



16 or 16  x 1


32 or 16 x 2









AT this point, I want to make sure that my students understand that larger unit can be divided into equivalent units as shown in the diagram above.  As the understanding increases they should ultimately understand that the same unit can be repeated to determine the additional measurements used in two step problems. (MP8) 



20 minutes

I ask students to move into their assigned groups. 

Moving the students deeper into understanding  how conversion works, I tell students we are going to do an exciting experiment to compare how the size of 1 ounce compare to the size of 1 pound.

Note: If students have not used a scale before do not forget to review how to use it.

Things you will need:

A loaf of bread, scale, pencil, and paper

Each group will work collaboratively to determine how larger units can be divided into equivalent units by comparing each unit.

I will begin by saying, “A slice of bread weighs about 1 ounce.  Some loaves of bread weigh about 1 pound. How many ounces does it take to make 1 pound?  16 Ok! If it takes 16 ounces to make 1 pound, then how does the size of 1 ounce compare to the size of 1 pound?

As the students are working, I make sure I jot down what they are thinking to determine if they understand.  Next, I ask students to weigh one slice of bread and record how much one slice weighs on their paper.   Students noted that one slice of bread weighed about 1 ounce.   You know a slice of bread weighs about 1 ounce.  Again, how many ounces do it takes to make a pound?  16 Can you illustrate on your paper how many slices of bread it would take to make 1 pound?

As students are working, I circle the room to check for understanding?  I notice several students drew 16 equal parts, and numbered them 1-16.  To probe a little deeper I ask students if 1 slice of bread weighed 1 ounce; how 1 ounce would compare to the size of 1 pound.


There are 16 ounces in 1 pound.  So, 1 pound is 16 times as heavy as 1 ounce.

I give students an additional 10 minutes to work in their groups.  I encourage them to openly discuss their thinking within their groups.


Independent Closing

20 minutes

To bring this lesson to a close, I ask students to return to their assign seats.  I give them about 10 minutes to share what they learned in their groups with the rest of the class.

 After that, I give them their exit ticket.  I give them a conversion chart labeled ounces and pounds. work sample 1 I ask them to figure out the amount of ounces for each given pound.  While students are working, I ask them if they were surprised by the weight of the slice of bread. What did you learn, and how can you use it in the future?

While students work, I walk around to check for understanding.  I notice that some students solve in different ways.  Some students use multiplication Work sample 2 and some use addition to convert ounces and pounds. to what they already knew and use it to help convert a smaller unit into a lager one.

student Response (video)