How Accurate?

Download the video and lesson plan by clicking here


  • To broaden children’s perception of length as the only linear measure, and include width, height, depth, thickness, perimeter, circumference, radius, diameter, distance and girth as examples of linear measures.
  • To involve children in decision-making and problem-solving and estimating linear measures in the appropriate units

Introducing the topic

  • Invite someone to attempt to draw a spiral on the blackboards that is about a meter long. ‘How can we measure it?’
  • Measure using a method offered by someone. Try to do one 2 meters long! Half a meter long! Does length have to be straight?

Questions during activities

  • What is that you are measuring?
  • What decisions have you needed to make?
  • How accurate do you think your answer is?
  • How accurate does it need to be?
  • What might you use to measure it?
  • What would be your units of measure?
  • How good was your estimate?

Things to think about

  • How long is a piece of elastic?
  • How tall is an aeroplane? (What would you measure?)
  • How thick is your skin?
  • How deep do you think the sea could be?
  • How do you decide what units to measure in?

Experiences to build on

  • Problem-solving / decision-making
  • Measuring with non-standard units

Organizational Points

  • Activities lend themselves to children working in pairs. Time to discuss results is important.

Assessment Observations

  • Ability to choose or devise appropriate units and measuring equipment
  • Ability to make reasonable estimates of unusually sized linear measures
  • Ability to decide for oneself how to approach a task, whether or not it is a successful method
  • Ability to discuss and reflect upon the process and results of measuring

Before showing children the video clip

  • Try drawing a spiral that is a meter long

What you may need

    3 books, plasticine, rulers, tapes, chalk, building blocks, string/wool

Things to do

  • Find 3 books with a range of thickness of paper used for the pages. Devise a way to measure and compare how thick the pages are in each book, as accurately as you can.
  • Make some plasticine shapes. Try to make one that has 10cm girth, another with 7cm height and examples of 2cm depth, 1cm thickness, 5cm width, 8cm length. See if someone else can sort out which is which.
  • Find at least 50 ways to measure the length of your stride using different ‘units’ eg strips of paper, tape measure, cubes, pencils, handspans, centimeters, feet, using comparisons … Is your stride always the same length?
  • Try building a tower on a table that is the same height as a tower on the floor. Try the same height on a chair.
  • Draw some circles on the playground using chalk, that have: 1m diameter; 1m circumference; 1m radius. Try to draw them about 1 meter apart too!

More activities

  • Design and make your own measuring equipment with a suitable scale to measure one of the following:
  • depth of puddles
  • diameters of tree trunks
  • width of feet
  • thickness of pencil leads
  • How far form the floor are your eyes when you are sitting down, standing up, lying down, jumping up …? Estimate, then measure.
  • Draw a number of boxes on a sheet of paper. Find the total length of black lines around all the boxes. Which two boxes are closest in the size of perimeters?

Ideas for the whole class

  • Take Body Measurements
    Collect data on linear body measurements for everyone in the class eg height, armspan, girth (round waist perhaps), length of stride, head-circumference, wrist circumference, handspan etc Use a computer if possible to analyse the data and to look for relationships eg ‘Is it true that approximately 3 times round your head is your height?’ ‘Do the tallest people have the longest stride?’ …
  • Book of Measurements
    Make a book of enormous and tiny linear measurements eg ‘How far is it to the moon?’ ‘How thick is a strand of hair?’
  • Make a collection of unusual measuring equipment.