Measuring Irregular Spaces for Carpet Installation

Male hands measuring and cutting carpet with blade

Measuring your room for carpet can get a bit tricky when you take irregular spaces into account. It’s all pretty straightforward when you’re just working with a square or rectangular room. Simply multiply the length of the room by the width, and you’ve got the amount of carpet in metres that you need to buy. But when it comes to irregular spaces, there’s a bit more to it.

At, 0420 Carpet we are Sydney’s experts in carpeting and other floor and window coverings. We sell a range of affordable and high-quality carpets and we love helping customers to make a great choice.

Below are some tips and calculations to follow for measuring different shaped rooms for carpet installation.

Divide Into Squares or Rectangles

If possible, divide the area into smaller rectangles and squares and then measure each area. Add up all of the squares together for your total amount of carpet needed.

Make sure to always add 10% to the total – this will account for waste and mistakes.

Triangular Rooms 

Triangular shaped rooms are most often found in attics. To tackle this space, start by finding the area. Measure the base length and then multiply this by the height of the room, or the distance from the top to the bottom sides. Multiply that height by up to a half to find the amount of carpet that you’ll need to buy.

For example, consider a room with a base of 10 metres and a height of 15 metres. Multiply them together, and you get 150 square metres of carpeting.

Trapezoidal Rooms

To carpet trapezoidal rooms, start by measuring both of the room’s parallel sides in metres. Then find the height of the room. Divide the height by two and add the length of the parallel sides together. Multiply this sum by the division of the height and you will have the amount of carpet you need to buy.

Consider a room with base dimensions of 10 metres and 15 metres. The height is 20 metres. Start by dividing 20 (the height) by 2, which is 10. Then add up 10 and 15, which equal 25. Finish by multiplying the two numbers – 25 x 10 =250 square metres of carpeting needed.


Rooms that are shaped like parallelograms are easier to measure than you’d think. Simply measure the base of the floor plan and multiply it by the height to find the amount of square metres of carpet you’ll need. This is similar to the way you measure for a triangular room. 

Have any other oddly shaped rooms that need carpeting? Why not come into our showroom in Sydney today. You can choose your very own carpet and speak with an expert for helpful tips and advice!