Paint and drywall
Paint volume and drywall sheets for rooms and walls.
Paint Calculator
Work out how much paint a room needs, with doors and windows taken out.
Drywall Calculator
Work out how many sheets of drywall a room needs, openings taken out.
Wallpaper Calculator
Estimate wallpaper rolls from wall width, drop height, roll size and pattern repeat.
Insulation Calculator
Estimate insulation packs from several wall or ceiling areas and the coverage on the pack.
Siding Calculator
Estimate siding cartons from wall areas, openings and the coverage on each carton.
Plaster and Render Calculator
Estimate wet plaster or render volume and bags from area, thickness and product yield.
Interior work is mostly arithmetic about surfaces, and the surfaces are smaller than they look. A room's four walls come to a large number until you take out the door and the windows, which on a small room can be a fifth of the total, or a whole extra tin of paint. Both calculators here subtract openings by default. Coverage is the figure worth checking rather than accepting. Paint spread rates on a tin assume a smooth, primed surface; bare plaster, filler and anything textured can use half as much again on the first coat. The advanced options let you type the number off your own tin. Neither calculator estimates screws, tape or joint compound. There is no figure for those that survives different stud spacings and techniques, and inventing one would be worse than leaving it out.