DIYCalc

Home-project material calculators — paint, tiles, flooring and concrete, from dimensions straight to what to buy and what it costs.

Material estimation has a rule that beginners skip: always buy an overage. Ten percent for paint and flooring, more for tiles laid diagonally or in a patterned room, because offcuts are waste and a second batch rarely matches the first — dye lots differ visibly in tile and paint alike.

The arithmetic that trips people is coverage versus area. Paint is sold by coverage per litre for one coat, and most colour changes need two, so the honest figure is double what the tin implies. Concrete is worse, since it is ordered by volume and a slab's depth is the term people most often get wrong.