How to Calculate Tile Wastage

“Wastage” is not waste in the careless sense - it is the extra tile you genuinely need for cut edges, breakages and future repairs. Set it too low and you run short; here is how to get it right.

Where the waste actually goes

Three places:

1. Cut tiles at the perimeter - few rooms are an exact number of tiles wide, so edges get cut and the offcuts often cannot be reused.
2. Breakages - a tile or two cracks during cutting or handling.
3. Spares - tiles kept back for repairs years later, when a fresh batch would not match.

The allowance by layout

The layout drives the percentage, because it changes how many tiles get cut:

Layout	Allowance	Why
Straight grid	10%	Cuts only at the room perimeter
Offset / brick / diagonal	15%	Every other row starts with a cut
Herringbone / chevron	20%	A diagonal cut at almost every edge

A straight grid is the most economical; the more angled and intricate the pattern, the more tiles meet the edge at an angle and the more offcuts you cannot reuse.

When to go to the high end

Push toward the upper figure (or beyond) when:

• the room is small or has lots of doorways, alcoves or fixtures - the perimeter is large relative to the area, so more tiles are cut,
• you are using natural stone, which varies between batches and is worth over-ordering, or
• the tiles are large-format, where a single bad cut wastes a big tile.

If your job does not fit a preset, the tile calculator has a Custom % option so you can enter exactly what your tiler quoted.

Worked example

A 10 m² bathroom floor in a diagonal layout:

1. Base tiles for 10 m² (say 0.36 m² tiles): about 28 tiles.
2. Diagonal layout → 15% allowance: 28 × 1.15 ≈ 33 tiles.

Those 5 extra tiles cover the angled perimeter cuts, a breakage or two, and a spare for repairs.

Next steps

Set the layout, then get the full count: see how many tiles do I need for the method, or jump straight to the tile calculator. Tiling a shower or splashback, where waste runs higher? Read how to measure a shower for tile.