Turns room measurements into the paint a repaint actually consumes, coat by coat.
Painting, tiling and finishes. 5 questions answered below, each with the arithmetic behind it and the limits of what the tool decides. Open the Paint Calculator tool.
A paint estimate answers one question with a number: how many tins do I buy? Everything else on the page exists to make that answer trustworthy. Wall and ceiling areas are measured separately because they take different products, openings are deducted because nobody paints a window, and the number of coats is yours to set because a refresh and a colour change are not the same job. The arithmetic is deliberately plain. Area to be painted, divided by the coverage the product states, multiplied by the number of coats, rounded up to the tin sizes your market sells. What makes the result usable is not the division but the discipline around it: coverage comes from the product record instead of an assumed spread rate, primer is priced as its own product with its own consumption, and waste is a stated percentage rather than a silent margin added to the litres.
Take a room four metres by three, with a ceiling height of two and a half metres, one door two metres wide by one high and one window one and a half metres wide by one high. The wall perimeter is fourteen metres, so the gross wall area is thirty five square metres. The door takes two square metres and the window one and a half, leaving thirty one and a half square metres of wall. The ceiling adds twelve square metres, and it is priced as its own surface. Painting the walls only, in two coats, with a product specifying twelve square metres per litre, needs two and seven tenths litres per coat, so five and four tenths litres in total, which rounds to two five litre tins. Change the product to one specifying ten square metres per litre and the same room needs six and a third litres, which is still two tins of five, but three if your market sells four litre tins. That is the whole point of the tool: the same room, a different product, a different order.
Two coats is the normal interior finish, and three when the colour changes sharply or the wall is patching bare plaster. The calculator applies the coats you choose and shows the litres for each one separately, so a single coat refresh is priced as a refresh. On a wall that has been skimmed, a mist coat first is usual practice, and it is priced as its own line because it consumes material without being part of the finish.
Measure the walls you are painting, deduct the openings you are not painting, then divide by the coverage the product states. The calculator does the measuring arithmetic and the division, then rounds up to the tin sizes sold where you are working. Two things decide the answer more than the area does: the product's coverage, which differs widely between a premium emulsion and a contractor grade one, and whether you are changing colour, which costs an extra coat.
Yes, and on their own lines, with their own coverage and their own quantities. A primer or undercoat is a different product from a topcoat, consumed at a different rate, and pricing it as extra topcoat litres produces an order that is short on one and long on the other. If you are painting over a sound, previously painted wall, leave them out of the estimate and the total drops accordingly.
Labour, masking, sanding, filling, caulking and any surface repair are outside this estimate, as are scaffolding and protection of floors and furniture. The estimate covers paint and primer quantities and their cost from the product records, which is the part you need before you go to the paint shop. It also leaves out any specialist product a substrate demands, because that is a specification decision rather than a quantity calculation.
Switch the unit and the area, coverage and tin sizes all convert together, so a building measured in feet and a specification written in litres still produce one order. The conversion happens on the factors rather than on the final figure, so a square metre never becomes a scaled length. Enter coverage in the unit you are working in and the division stays in one system, which is what prevents the doubling errors that come from converting twice.