Painting & decorating calculators & guides
Free painting & decorating tools and plain-English guides for New Zealand — each gives the answer fast and shows the working behind it.
About painting & decorating calculations
Painting and decorating is mostly an estimating problem before it is a brush-and-roller one. How much paint covers a room at the spread rate on the tin, how many rolls of wallpaper go round the walls, how much filler and primer the prep needs — each is a measurement question where a few room dimensions decide what to buy and how much it costs. Wallpaper in particular punishes a rushed estimate, because it is hung in full-height strips and the offcut at the end of each roll is waste.
The decorating tools here handle that arithmetic and the waste that goes with it, showing the working so you can see how the room size, the wall height and the pattern repeat change the count. They take dimensions in feet or metres and convert as needed, because paint and paper arrive in both imperial and metric sizes depending on the brand and country.
Using the results
Treat the quantities as shopping figures, not guarantees. Coverage varies with the surface, the colour and the number of coats, and wallpaper rolls vary in length and width by brand, so read the tin or the roll label and adjust. The number here tells you how much to buy; surface preparation, priming and buying every roll in one batch so the shade matches are the parts that decide whether the finish looks right, so plan those alongside the order.