You’ll need to work out the following…
- Surface area (excluding windows and doors).
- Spreading Rate of the paint.
- The number of coats required.
The basic rule-of-thumb formula for the number of paint litres needed is: Surface Area divided Spreading Rate per litre multiplied by the Number of Coats.
SA ÷ SR × NC = Paint litres needed
Before You Start
Budget for top-quality paints. Quality paints don’t just give you a better look. They’re easier to apply, give better coverage, last longer and are a lot easier to clean than budget options.
Similarly, good quality paint rollers and paintbrushes will give you a superior finish.
Calculate The Area of a Room
To figure out the area of a rectangular room with standard size windows and doors, do the following:
- Measure the width and length. Adjust each figure to the closest half-meter, then add them together.
- Multiply the total by the room height and then double that result. The final figure is the area of your walls in Sq m.
- From the area figure, subtract 1.5 Sq m for each of the windows and 2 Sq m for each door.
Ceiling area is simply the width multiplied by the length of the room.
What About an Oddly-Shaped Room?
If you need to calculate the area of an oddly-shaped room, simply break the room into smaller rectangles using the above method, then add them together.
What About Trims and Skirting Boards?
Calculate these areas individually by multiplying the width or height by the length for each, then add your totals together.
What About Doors and Window Frames?
Allow 2 Sq m for each side of a door and 1.5 Sq m for a single size window frame.
How Does Coverage Affect the Total?
At the point you know the total area you will cover, you must half the information you need to order paint. The rest relies upon the Spreading Rate of your paint and the surface it must cover.
If your surface is smooth, estimate on a Spread Rate of between 12–16 Sq m with a litre of paint. Divide your area figure by the Spread Rate to arrive at the number of litres you’ll need for your first coat. If you intend to paint on rough, porous or previously unpainted walls, a litre will cover notably less than that. However, you can count on more coverage for the second coat.
Always check the coverage information on the label of the paint can, as various types of paint will have different spreading limits.
Take the guesswork out of it and use the free Dulux Paint Calculator.