Perimeter
Calculate perimeter of squares and rectangles
What is Perimeter?
Perimeter is the total distance around the outside of a shape. To find the perimeter, add up the lengths of all the sides. We measure perimeter in units like millimetres (mm), centimetres (cm), and metres (m).
Example
Finding Perimeter
Rectangle: length = 8 cm, width = 5 cm
Perimeter = 8 + 5 + 8 + 5 = 26 cm
Or use the formula: P = 2 × (length + width) = 2 × 13 = 26 cm
Square: side = 6 cm
Perimeter = 6 + 6 + 6 + 6 = 24 cm
Or: P = 4 × side = 4 × 6 = 24 cm
Example
Irregular Shapes
A shape with sides: 3 cm, 5 cm, 4 cm, 7 cm, 2 cm
Perimeter = 3 + 5 + 4 + 7 + 2 = 21 cm
Just add ALL the sides!
Note
Remember
Perimeter is always measured in units of length (cm, m, etc.). For a rectangle, you can use P = 2 × (l + w). For a square, P = 4 × s. For other shapes, add all sides together.
Key Vocabulary
PerimeterThe total distance around a shape
LengthHow long something is
WidthHow wide something is
CentimetreA unit of measurement (cm)
FormulaA rule written with numbers and symbols
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Perimeter
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