Tile calculator

How the tile count is worked out

Each tile plus half the joint on every side covers a module of its own size plus the joint. Dividing one square metre by that module gives the tiles per square metre.

A 300 mm tile with a 3 mm joint covers 0.0918 square metres, which is 10.89 tiles per square metre. Without the joint it would be 11.11, so the joint saves about 2 per cent.

The waste allowance is added after that, and the count is rounded up because tiles are bought whole.

Worked example

Twelve square metres of 300 mm tiles with a 3 mm joint needs 131 tiles before waste, and 144 with 10 per cent added.

Large format tiles waste more, not less. A 600 mm tile cut at a wall leaves a bigger offcut, so use 15 per cent for a room with several walls and a doorway.

Waste, cuts and spares

Ten per cent covers normal cutting around the perimeter. A diagonal layout, a herringbone pattern or a room with many obstacles needs 15 per cent.

Keep a box spare. A tile that cracks in five years will not be in the same shade or calibre, and a different batch shows.

Boxes are sold by coverage, not by tile count, so divide the total by the box coverage to see how many boxes to order.

Limits of this calculator

It measures flat area. It does not account for a window reveal, a skirting cut, a border or a mosaic insert, which need their own measurements.

It does not include adhesive or grout, which are separate quantities with their own coverage figures.

It does not check the substrate, the movement joints or whether the tile is suitable for the location.

For a painted finish above the tiles, use the paint calculator.

Inputs for the tile calculator