Topic outline

  • Outcomes

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    In this course you will learn about:

    1. The definition of mass.
    2. The difference between mass and weight.
    3. Different units of measure for mass.
    4. How to convert between different units of mass.

    • In this course we will explore the units of mass but before we dive into the nitty gritty of this topic, do you understand what mass is?


      The amount of mass present in an object will make that object either light or heavy.

    • Is mass the same as weight?

      This is a very good question! Many people use the word mass and weight interchangeably but they actually have very different meanings!

      You already know that mass is the amount of matter in a particle, object or body, so what is weight?


      Watch the YouTube video below which clearly explains this important difference.

      Badzilla. (2020). The difference between mass and weight (Standard YouTube licence)

    • How is mass measured?

      Using the metric system, the most common units used to measure mass are:

      • Milligram (mg)
      • Gram (g)
      • Kilogram (kg)


      The gram is the metric base unit for mass.

      It's important to understand what the prefixes mean in units of measurements: [edit: please change one-thousandths to one-thousandth (singular) in the artwork below]


      Using the information provided above, this means that:

      • 1000 mg = 1 g or to put this another way: 1 mg = 0.001 g
      • 1000 g = 1 kg or to put this another way 1 g = 0.001 kg

      Understanding what the prefixes mean will assist you when converting one unit of measure to another.

      Watch the YouTube video which explains clearly how mass is measured and how to convert between the different units of mass.

    • ClickView. (2022). What unit is mass measured in? (Standard YouTube licence)


      Test your understanding of what has been covered so far, by answering the questions in the short quiz below.

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  • Working with different units of mass

    • Converting between different units of mass

      Take note of the following rule when converting between different units of measurement:

      • When converting from larger to smaller units, you will multiply by the relevant power of 10
      • When converting from smaller to larger units, you will divide by the relevant power of 10. 

      Let's illustrate this point when referring to units of mass:


    • Conversion examples

      Let's look at some examples of how to convert between different units of mass:

      Example 1



      Ali would like to know how many grams are in this 8 kg bag of sugar. 


      First, figure out if you are converting from a smaller unit to a larger unit or a larger unit to a smaller unit. In this scenario you are converting kilograms to grams, which is a larger unit to a smaller unit. You will therefore have to multiply (remember: large to small = multiply, small to large = divide).

      8 kg x 1000 = 8000 g

      Example 2


      Adiva needs to make broccoli soup to feed 10 people. For this large number of people, the recipe states that she requires 2500 g of broccoli. However the market only sells broccoli in kg. How many kg should Adiva request?

      First, determine whether you are converting from smaller units to larger units, or from larger units to smaller units. In this example, we are required to convert from small to large and that means that we will need to divide:

      2500 g รท 1000 = 2.5 kg

      Adiva will need to request 2.5 kg of broccoli! Would you eat this soup?!

      Now watch the YouTube video below which illustrates further conversion examples.

    • Math with Mr J. (2020). Converting metric units of mass (Standard YouTube licence)

    • Comparing different units of measure

      Knowing how to convert different units of measure to a larger or smaller unit is very useful, especially when you are required to compare, in this case, the mass of different objects. Let's explore how to compare by way of an example:

      Ridwaan is playing a math game on the computer. He has to compare metric units by filling in the blank with the correct sign. His choices are greater than (>), less than (<), or equal to (=). This is the problem Ridwaan is working on:

      • 5.5 g _________ 4500 mg


      The following steps will be used to solve this problem:

      1. Convert 5.5 g to mg. You are converting a larger unit to a smaller unit so you will multiply: 5.5 g x 1000 = 5500 mg
      2. Substitute 5500 mg for 5.5 g in the original problem and compare: 5500 mg ______ 4500 mg
      3. Now it's easy to compare since both the numbers are in the same unit i.e. mg.
      4. The solution therefore is: 5.5 g > 4500 mg


      Did you get the above answer?


      Answer the questions in the short quiz below to test whether you understand what was covered in this section - good luck!

    • Quiz icon
      Test your knowledge Quiz
      Receive a grade Receive a passing grade

    • Summary

      Having now completed this course on the metric units of measure for mass, you should now be comfortable with:

      • understanding the difference between mass and weight
      • the various units of measure for mass
      • converting between different units of mass
      • comparing different units of mass.


      And remember:



    • Attribution

      The following resources were consulted:

      • CK-12 Foundation. (2022). Equivalent metric units of mass. Available online here. (CC BY-SA)
      • CK-12 Foundation. (2022). Conversions of length, mass and capacity in metric units. Available online here. (CC BY-SA)
      • Badzilla. (2020). The difference between mass and weight (Standard YouTube licence)
      • ClickView. (2022). What unit is mass measured in? (Standard YouTube licence)
      • Math with Mr J. (2020). Converting metric units of mass (Standard YouTube licence)