# Perimeter of Rectangle

To calculate the **perimeter of a rectangle** we need to know a length of all its sides. A rectangle has two opposites sides with same length so you can know only the length of its adjacent sides. If rectangle´s adjacent sides are same (it means all sides are same), it is a square. The **perimeter of a rectangle** is a phrase which means a total sum of all sides length. For example a length of a fence around a rectangular garden. The elementary unit is one metre (1 m).

## Perimeter of Rectangle - formula

**Perimeter of Rectangle** = 2 × (side length a + side length b)

P = 2 × (a + b), where a ≠ b