Area and Perimeter: Measuring Perimeter — Year 4 Lesson Plan
National Curriculum: Mathematics — Measurement, Year 4: measure and calculate the perimeter of a rectilinear figure (including squares) in centimetres and metres
Overview
The first of four Area and Perimeter lessons. Pupils learn that perimeter is the distance all the way around the outside of a 2-D shape. They measure each side of rectangles, squares and other rectilinear shapes with a ruler, add the lengths to find the perimeter, and measure larger perimeters in metres.
Area and Perimeter: Measuring Perimeter learning objectives
- Explain that perimeter is the distance all the way around the outside of a 2-D shape.
- Measure the sides of rectilinear shapes in centimetres and add them to find the perimeter.
- Choose centimetres or metres to measure the perimeter of everyday objects and spaces.
Success criteria
- I can explain what perimeter means.
- I can measure each side of a shape with a ruler, starting from 0.
- I can add all the sides to find the perimeter, ticking each one so I don't miss any.
- I can choose centimetres or metres to measure a perimeter.
Key Vocabulary
Suggested Lesson Structure
Show a book and ask: if an ant walked all the way around the edge of the cover, how far would it walk? Pupils trace the edge of their own book with a finger and estimate the distance in centimetres. Introduce the word perimeter: the distance all the way around a shape.
Model measuring a rectangle 8 cm by 5 cm: line the ruler up from 0, measure each side and label it. Add all four sides: 8 + 5 + 8 + 5 = 26 cm. Then show an L-shaped rectilinear shape with six sides. Mark a starting corner and tick each side as it is added so none is missed. Show that a square has four equal sides. Discuss units: centimetres for small objects such as a book, metres for large spaces such as the classroom or playground.
In pairs, pupils measure the perimeter of printed rectangles, squares and L-shapes, marking a start corner and ticking each side. Pairs compare answers; where they differ, discuss why (not starting at 0 on the ruler, missing a side, rounding to the nearest centimetre).
Pupils estimate and then measure the perimeter of classroom objects (an exercise book, a whiteboard, a table top), choosing centimetres or metres, and record them in a table. Some pupils measure part of the classroom or playground with a metre stick or trundle wheel. Challenge: draw a rectilinear shape with a perimeter of exactly 20 cm.
Hinge question: a rectangle has sides of 6 cm and 3 cm. Sam says the perimeter is 9 cm. What has Sam done wrong? (Added only two sides; the perimeter is 6 + 3 + 6 + 3 = 18 cm.)
Video for this lesson
Measuring Perimeter | Year 4 Area and Perimeter, Lesson 1 | KS2 Maths (No Narration)
What perimeter means, measuring each side of a rectangle with a ruler from 0, ticking each side of an L-shape so none is missed, squares, and choosing centimetres or metres. The words are on screen, so you can pause and talk it through. Ends with a three-question quiz.
Watch on YouTube →Support and extension for area and perimeter: measuring perimeter
Support
- Work on centimetre-squared paper with whole-centimetre sides so lengths are easy to read.
- Give a recording frame with one box per side: “___ + ___ + ___ + ___ = ___ cm”.
- Use string laid around the edge of a shape, then straightened and measured, to show the idea of perimeter.
Extension
- Draw a rectilinear shape with a perimeter of exactly 20 cm, then a different one with the same perimeter.
- Measure the perimeter of the classroom in metres and explain how you made sure the measurement was accurate.
- Estimate the perimeter of three objects before measuring and explain how close each estimate was.
Check for understanding
Quick questions for the plenary or an exit ticket. Tap a question to see the answer.
1. What is perimeter?
Answer: The distance all the way around the outside of a 2-D shape.
2. A rectangle measures 8 cm by 5 cm. What is its perimeter?
Answer: 8 + 5 + 8 + 5 = 26 cm.
3. A square has sides of 7 cm. What is its perimeter?
Answer: 28 cm.
4. Would you measure the perimeter of the playground in centimetres or metres?
Answer: Metres, because it is a long distance.
Resources you will need
- Rulers and metre sticks (a trundle wheel if available)
- Printed rectangles, squares and L-shapes with whole-centimetre sides
- String for the support activity
- Exercise books, whiteboards and table tops to measure
- Recording table for the independent task
Common Misconceptions
- Adding only two sides of a rectangle. Every side must be added; tick each one as you go.
- Measuring from the end of the ruler instead of from 0.
- Missing a side of an L-shape or other rectilinear shape with more than four sides.
- Thinking perimeter is the space inside a shape. That is area; perimeter is the distance around the edge.
Prior Knowledge
Pupils should already be able to:
- Measure the perimeter of simple 2-D shapes (Year 3).
- Measure lengths in centimetres and metres using a ruler or metre stick (Years 2 and 3).
- Add several numbers together, including two-digit numbers (Year 3).
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