# How to Calculate How Much Paint to Buy Whether you plan to paint a bedroom, the entire interior, or the exterior of your home, you’ll need to calculate how much paint to buy. Buying too much paint is a waste of money, and buying too little paint is a total headache, so 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 is a fairly simple calculation.

First, 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 square metres

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

Now, consider the number of doors and windows. For each door, subtract 1.9 square metres, and for each window, subtract 1.4 square metres. 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 square metres

Total paintable surface = 24 – 4.7
= 19.3 square metres

## How Much Paint to Buy

As a general rule, 1 litre of paint will cover between 6 and 6.5 square metres 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 Considerations

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 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. 