Tile Count Calculator

The formula this calculator uses

Tiles = (room area / tile area) x (1 + wastage)

A

Area to be covered, in square metres

a

Area of one tile, in the same square unit

w

Wastage rate as a decimal, commonly 0.1 for ten percent

N

Tiles to order, rounded up to a whole number

How to check the result by hand

1. 1

   Measure the surface in one consistent unit

   Measure the length and width of the floor, or the height and width of the wall, and write both down in the same unit. A room 4 metres by 3 metres gives 4 and 3. If the tape reads in centimetres, convert to metres first, because the tile side will be quoted in metres and the two figures must agree before any division is attempted.

2. 2

   Multiply to get the area to be covered

   Multiply length by width to get the surface area: 4 x 3 = 12 square metres. If the space is not a simple rectangle, split it into rectangles, compute each one and add the results. Subtract the areas of permanent obstructions such as fitted units or a fixed bath only if they will never be tiled behind.

3. 3

   Compute the area of a single tile

   Multiply the tile side by itself for a square tile: 0.3 x 0.3 = 0.09 square metres. Rectangular tiles use length times width instead, so a 0.3 by 0.6 metre tile covers 0.18 square metres. Write this figure down separately, because it is the divisor for the next step and the most common place for a unit slip.

4. 4

   Divide the surface area by the tile area

   Divide the surface area by the area of one tile: 12 / 0.09 = 133.33333333333334. That decimal is the exact number of tiles the geometry demands, with no allowance for cuts or breakage. Keep the full value rather than rounding it here, because rounding too early carries the error into the wastage multiplication that follows.

5. 5

   Add wastage, then round up to a whole tile

   Multiply the exact count by one plus the wastage rate: 133.33333333333334 x 1.1 = 146.66666666666669 for ten percent. Round that up to 147 tiles, never down, and convert to boxes if the tiles are sold in packs. Order the rounded figure and keep the surplus tiles for future repairs.