DIY calculators that show their working

Work out how much paint, tile, concrete or timber to buy before you head to the hardware store. Every calculator explains the maths and the assumptions behind it.

Walls and ceilings

Paint, wallpaper and plasterboard for a room.

Paint Calculator How many litres of paint for walls and ceilings, allowing for doors, windows and coats.Wallpaper Calculator Rolls of wallpaper for a room, allowing for the pattern repeat, doors and windows.Plasterboard Calculator Sheets of plasterboard for walls and ceilings, less doors and windows, plus offcuts.

Floors and tiles

Floor area in square metres, tiles and flooring packs.

Tile Calculator Tiles and boxes for a floor or wall, with grout joints and a waste allowance.Flooring Calculator Packs of laminate, vinyl or timber flooring for a room, plus skirting and underlay.Square Metre Calculator Floor area of rooms of any shape in square metres, with square feet alongside.

Garden and concrete

Slabs, footings, mulch, garden soil and gravel.

Concrete Calculator Concrete for slabs, footings and post holes, in cubic metres and bags of premix.Mulch, Soil and Gravel Calculator Mulch, garden soil, gravel or sand to cover an area, in cubic metres, bags or tonnes.

Timber, stairs and roofs

Timber lengths and volume, stair layout and roof pitch.

Timber Calculator Timber in lineal metres and cubic metres, priced per metre or per cubic metre.Stair Calculator Number of steps, riser height, going and stringer length, checked against the NCC.Roof Pitch Calculator Convert roof pitch between degrees, percent and rise over run, and work out rafter length.

More tools (US version)

These tools are written for the United States, with US units first. They open in the US English version.

Feet and Inches Calculator ENAdd and subtract imperial lengths in feet, inches and fractions, and convert them to millimetres.

How these calculators work

The formula is on the page

Each calculator explains how the result is worked out, with an example you can check by hand.

Figures come with a source

Paint spread rates, product sizes and building rules link to the page we checked, with the date we checked it.

What you type stays on your device

Everything is calculated in your browser. There is no account, and nothing you type is sent to us.