Measuring Perimeters

Measure the perimeter of simple 2-D shapes

ages 7 to 88 practice questionsvideo included

What a learner can do afterwards

Measure each side of a rectangle and add the lengths to find the perimeter
Calculate the perimeter of a regular shape given the side length
Explain that perimeter is the total distance around a shape

The lesson

The perimeter of a shape is the total distance all the way around its outside edge. Imagine walking along every side of a shape, from your starting corner back to the same spot. The distance you walk is the perimeter.

This rectangle has sides 5 cm, 3 cm, 5 cm, and 3 cm. Add them all: 5 + 3 + 5 + 3 = 16 cm.

Try it together

Leo measures a small garden bed. Two sides are 6 m long and two sides are 4 m long. He adds 6 + 4 + 6 + 4 and gets 20 m. That is the perimeter of his garden bed.

Good to know

If a shape is regular, all its sides are the same length. To find its perimeter fast, multiply the side length by the number of sides. A square with 4 cm sides has a perimeter of 4 x 4 = 16 cm.

Perimeter is the distance all the way around a shape: add up every side to find it.

Watch it

Where it sits

Learn first

Calculating with measurements 2-D shapes (age 6+)

This opens up

Perimeters of polygons

Where this leads

Jobs that lean on this skill. Follow one to see everything it is built on.

Air Traffic Controller Artist Astronaut Athlete Baker Botanist

Then practise

8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.