How to Calculate How Much Paint to Buy

To calculate how much paint to buy, measure your wall surface area, subtract doors and windows, then divide by 6.5 — that gives you the number of litres needed per coat. It takes less than five minutes and prevents the most common DIY mistake: overbuying paint that dries up in storage before you ever use it.

Below, Brisbane's residential painters walk you through the exact formula, with a worked example you can apply to any room.

How to Measure Your Paintable Surface Area

The first thing you will need to do is calculate the surface area you plan to paint. This surface area should include all of the walls and even the doors if you plan to paint them. .

First, you will need to measure the length of each wall, and add them together. This is the perimeter of the room. Then, measure the height of the wall. Multiply the perimeter and the height, and you’ve calculated the total surface area of the walls in your room. To illustrate, imagine the perimeter of the room 12m, and the height of the walls is 2m.

12m x 2m = 24 metres squared

The total surface area of your room is 24 metres squared.

Next, consider the number of doors and windows. For each door, subtract 1.9 metres squared, and for each window, subtract 1.4 metres squared. Say this room has one door, and two windows. The total paintable surface can be calculated as follows:

Door and window surface area = (1 x 1.9) + (2 x 1.4)
= 4.7 metres squared

Total paintable surface = 24 – 4.7
= 19.3 metres squared

 How Much Paint Do You Actually Need?

As a general rule, 1 litre of paint will cover between 6 and 6.5 metres squared of wall.

So, to calculate how many litres of paint you will need, divide the total paintable surface area by 6.5. Let’s return to the example above, and calculate how much paint is required.

Paint required = paintable surface area / 6.5
                         = 19.3 / 6.5
                         = 2.97 litres

For this example, you’ll need to purchase 3 litres of paint.

Other Things to Consider Before You Buy

There are a few things you’ll need to consider when calculating how much paint to buy.

• Are you repainting a wall, or painting bare drywall? Drywall will absorb more paint, which means you’ll need to buy slightly more paint, even if you’ve coated it with a primer.
• Are you painting in a light or dark colour? If you’re using a dark colour, you will probably require a tinted primer, too.
• Don’t forget about future retouches. Always round the required amount of paint up, because you can use that paint in the future to touch up and remove stains and areas of wear and tear.

 Use the Dulux Paint Calculator

Instead of making these calculations yourself, the Dulux Paint Calculator is a handy free tool. Simply enter your room's dimensions, number of windows, and number of doors and it will do the work for you.

Once you know how much paint you need, Kraudelt Painting can help Brisbane and Gold Coast homeowners source the right product and get the job done professionally.

Hire Professional Painters in Brisbane & Gold Coast

The easier option is to leave it all to us, the professional commercial painting and house painters Brisbane and Gold Coast locals trust. We can answer all of your questions, including how much paint to buy, how long does it take to paint a room, and more.

Contact us for a quick and accurate quote. Give us a call on 0423 018 747 or fill out the form on this page.