How to calculate how much wall paint you need
Start with area, then use the coverage of the actual product and the number of coats. Here is where calculators most often go wrong.
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Basic formula
For a room, add the lengths of all walls to be painted and multiply the resulting perimeter by the height. Then subtract large windows and doors. This gives an approximate area for one coat.
- wall area = perimeter × height;
- minus openings that will not be painted;
- multiply by the planned number of coats;
- divide by the coverage stated by the paint manufacturer.
Why one universal coverage number does not work
Coverage depends on the formula, substrate, and application method, so there is no universal consumption figure for every paint. Calculate the surface area, account for the number of coats, and divide by the coverage of the exact product. The value on the label or technical data sheet is more reliable than an average figure from a generic guide.
What increases actual paint use
- rough or textured surfaces;
- a porous, unprimed substrate;
- a high-contrast color change;
- an additional coat for an even result;
- losses on tools and application-specific factors.
Should you buy a small reserve?
A sensible small reserve helps you finish a wall without switching batches and leaves some paint for future touch-ups. A large uncalculated surplus is wasted money. Calculate the area first, then round to the actual can sizes of the chosen product.
Try it in practice
Calculate paint quantity
Enter the room dimensions and get an estimated quantity for your project.
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