It's important to work this out accurately because buying too much paint will leave you with a whole bunch of paint cans that will remain untouched in your outdoor shed or garage. The terrible thing about this is that it will most likely dry up and be completely unusable before you even work out when you'll most likely be using it. In the end, it's a total waste of your hard-earned money.
The bottom line is that you’ll want to ensure your estimate is accurate.
Here’s how to calculate how much paint to buy.
Measuring the 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're planning to paint them. Now, it's fairly easy to calculate this.
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.
Now, 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 to Buy
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.
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.
Here’s a Short Cut
Instead of making these calculations yourself, head over to the Dulux Paint Calculator. From there, simply type in your room’s dimension, the number of windows, and the number of doors and the calculator will do the work for you.
Call in the Professionals
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.