1. Construction Numeracy
Calculating Perimeters: Basic Shapes
Stonemasonry Department 2012

2. Perimeter
‘Perimeter is the distance
around a two dimensional
shape, or the
measurement of the
distance around
something; the length of
the boundary.’
Wikipedia 2012

3. Perimeter of a Square
5m
Perimeter = 5 + 5 + 5 + 5
Perimeter = 20m
5m 5m
or
Perimeter = 5 x 4
Perimeter = 20m
5m
To calculate the perimeter of a square we add the lengths of
each of the four sides. Because the sides of a square have
identical lengths we can use the following formula:
Perimeter of a Square = Length of One Side x 4

4. Perimeter of a Square
6m
Perimeter = Length of one side x 4
6m
Perimeter =
7m
Perimeter = Length of one side x 4
7m
Perimeter =

5. Perimeter of a Square
3m
Perimeter = Length of one side x 4
3m
Perimeter =
9.4m
Perimeter = Length of one side x 4
9.4m
Perimeter =

6. Perimeter of a Rectangle
6m
Perimeter = 6 + 4 + 6 + 4
4m Perimeter = 20m
To calculate the perimeter of a rectangle we add the lengths of
all four sides. Remember to use the correct unit of
measurement when displaying your answer (e.g. m, mm, cm,
km)

7. Perimeter of a Rectangle
8m
P = Side 1 + Side 2 + Side 3 + Side 4
6m Perimeter =
9m
P = Side 1 + Side 2 + Side 3 + Side 4
8m
Perimeter =

8. Perimeter of a Rectangle
3m
P = Side 1 + Side 2 + Side 3 + Side 4
2m Perimeter =
5.2m
P = Side 1 + Side 2 + Side 3 + Side 4
3m
Perimeter =

9. Perimeter of a Triangle
Perimeter = Side 1 + Side 2 + Side 3
6m 6m Perimeter = 6 + 6 + 6
Perimeter = 18m
6m
To calculate the perimeter of a triangle you add the lengths of
each of the three sides. You cannot assume that each side will
have the same length so check your answer carefully.

10. Perimeter of a Triangle
Perimeter = Side 1 + Side 2 + Side 3
4m 4m
Perimeter =
4m
8m Perimeter = Side 1 + Side 2 + Side 3
8m
Perimeter =
6m

11. Perimeter of a Triangle
Perimeter = Side 1 + Side 2 + Side 3
9m 9m
Perimeter =
8m
7m Perimeter = Side 1 + Side 2 + Side 3
7m
Perimeter =
8m

12. Perimeters of Complex Shapes
Perimeters are commonly used in the construction industry and
often the shapes we measure the perimeter of are not perfect
squares, rectangles and triangles but a combination of a
number of them. Can you calculate the perimeter of the shape
shown above?

13. References
The image on the title slide of this presentation was
sourced from Eric Gjerde’s photostream at:
http://images.cdn.fotopedia.com/flickr-153047995-hd.jpg
This image was made available under creative commons
The definition of perimeter was sourced from wikipedia at:
http://en.wikipedia.org/wiki/Perimeter

14. Developed by The Stonemasonry Department
City of Glasgow College
2012