## How to calculate the area of an octagon

There area two main methods to calculate the area of an octagon.

### Method 1:

If you know the length of “H” as well as “B” the length of one of the 8 sides, then you can use this method.

The octagon is made up of 8 triangles, so find the area of one triangle and multiply by 8.

## Example

The total height** “A”** of the octagon is 16.9m and the length of a side “**B**” is 7m, calculate the area. **A = 16.9m****B = 7m** First calculate the area of one triangle **Area of a triangle = 0.5 x Base x Height ****The height of one triangle = A ÷ 2 = 16.9 ÷ 2 = 8.45****Area of a triangle = 0.5 x Base x Height****Area of a triangle = 0.5 x 7m x 8.45 = 29.575m ^{2}**

**There are 8 triangles in an octagon, so 29.575m**

^{2}x 8 = 236.6m^{2}**Answer = 236.6m**

^{2}## Method 2:

You can use method two if you only know the length of one of the 8 sides.

## Example

The length of one of the 8 sides “**B**” is **7m**, calculate the area of the octagon. **B = 7m****The area of an octagon = 2 x (1 + √2) x B ^{2}**

**Area = 2 x (1 + 1.414213562) x 7**

^{2}**Area = 2 x (1 + 1.414213562) x 49**

**Area = 2 x (2.414213562) x 49**

**Area = 4.828427124 x 49**

**The area of an octagon = 236.6m**

^{2}