Skip to main content
Bunnings
Lowest Price Policy^
Spend & Earn Rewards

How to calculate square metres

A neatly landscaped backyard features a wooden deck with a small tree

Overview

Whether you're planning a renovation, buying materials, or figuring out the size of a space, knowing how to calculate square metres is an essential skill. It helps you estimate costs, plan layouts, and make sure you buy just the right amount of material—no more, no less.

This guide will show you how to calculate square metres for any room or surface, taking the guesswork out of your next D.I.Y. project.

Safety tip: Always wear the appropriate safety equipment (safety glasses, gloves, ear muffs and a mask, for example) and always follow the instructions for the product or equipment.

Tools and materials

    Steps

    1. 1

      Square metres for a rectangular area

      Measure the length and width

      Let’s begin with the simplest scenario: a rectangular space. Use your measuring tape to measure the length of the space in metres. Place the tape from one end to the other, ensuring the tape is straight for an accurate measurement

      Tip: Measure along the ground, as measuring at an angle may give inaccurate results.

      Next, measure the width of the space in metres. Again, ensure the tape measure is straight and flat to get an accurate measurement.

      Multiply the length by the width to get the total square metre size. For example: 5 metres × 4 metres = 20 square metres. It’s as simple as that! Knowing this measurement is particularly helpful when planning to buy flooring, paint, or even turf.

      A person in a red T-shirt is sketching a labeled diagram of length and width in a notebook while holding a pencil and measuring tape.
    2. 2

      Square metres for an irregular shape

      Break down the area

      If the area you’re measuring has an irregular shape, such as an L-shaped room or a garden with a nook, break it down into smaller rectangular sections. Measure each section individually

      Tip: It may help to sketch the area and divide it visually into rectangles before measuring.

      Measure the length and width of each rectangular section separately. Record the measurements in metres.

      A Bunnings Team Member is measuring the length of a lawn using a tape measure near a wooden deck in a garden.

      Calculate the square metres for each section

      Calculate the square metre size for each section by multiplying length by width, just as you would for a standard rectangle. For example: The main section is 3 metres × 5 metres = 15 square metres and the additional section is 2 metres × 2.5 metres = 5 square metres.

      Add them together to get the total area. For example: 15 square metres + 5 square metres = 20 square metres.

      A person in a red shirt is drawing labeled diagrams calculated square meters areas for each section in a notebook while standing outdoors.
    3. 3

      Estimating for curved or complex shapes

      For curved or uniquely shaped spaces, like garden beds or patios, it’s often easiest to approximate. Imagine the shape as a rectangle that covers the largest part of the area. Measure and calculate it as if it were a rectangle. While not 100% precise, this method will give you a close enough estimate for most D.I.Y. projects.

      Tip: If precision is important, consider breaking the complex shape into smaller rectangles or use a flexible measuring tape to better follow the curves.

      If your measurements are in centimetres, convert them to metres before calculating. Simply divide the measurement in centimetres by 100. For example: 450 cm = 4.5 metres.

      DIY - step 4 - How to calculate square metres
    4. 4

      Now that you’ve worked out the size of your space...

    Get inspired by projects from the Bunnings Workshop community

    Health & Safety

    Please make sure you use all equipment appropriately and safely when following the advice in these D.I.Y. videos. You need to be familiar with how to use equipment safely and follow the instructions that came with the equipment. If you are unsure, you may feel it is safest to consult an expert, such as the manufacturer or an expert Bunnings Team Member.

    Grave health hazards are linked to asbestos, which may be in homes built up to 1990. Health hazards may result from exposure to lead-based paints in older materials and copper chromium arsenic (CCA) treated timber. For information on the dangers of asbestos, lead-based paint and CCA treated timber and tips for dealing with these materials contact your local council's Environmental Health Officer.