Perimeter calculation questions: clear steps for 11+ GL & CEM
22 October 2026
Understanding perimeter
Perimeter is the total distance around the edge of a shape. It is a key skill for 11+ GL & CEM maths exams and comes up in many question types.
To find the perimeter, add up the lengths of all sides of the shape.
How to calculate perimeter
For simple shapes like rectangles, use the measurements given for each side. Make sure to include every side, even if some are the same length.
Worked example: perimeter of a rectangle
A rectangle has side lengths of 5 cm and 4 cm.
First, add the two long sides: 5 cm + 5 cm = 10 cm
Next, add the two short sides: 4 cm + 4 cm = 8 cm
Now, add both results: 10 cm + 8 cm = 18 cm
The correct answer is 18 cm.
Compound shapes and extra practice
Some questions use compound shapes. Always count every side, even if the shape is not regular.
For more perimeter calculation questions, try the perimeter package on our website.
Key insight: Perimeter is a basic skill that appears often in 11+ GL & CEM exams. Practising with different shapes builds confidence and accuracy.
