What wastage percentage should I allow for tiles?

For straightforward rectangular rooms with straight cuts, 10% wastage is standard. Allow 15% for rooms with many cuts (L-shapes, alcoves) and 20% for diagonal or herringbone patterns. It is always better to over-order slightly, as matching tiles from the same batch later can be difficult.

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Tile Calculator

Calculate exactly how many tiles you need, how many boxes to buy and the total cost. Accounts for tile size, grout gap, wastage percentage and partial tiles.

Grout Gap Included Cost Estimate

Room / Area

Room Length (m)

Room Width (m)

or enter total area directly

Total Area (m²) Enter room dimensions above OR type a total area here — whichever you fill last takes priority.

Deductions — cabinets / obstacles (m²) optional

Tile Details

Tile Length (mm)

Tile Width (mm)

Grout Joint (mm)

Wastage %

Tiles per Box

Price per Tile optional

Room area—

Net area to tile—

Tile area (incl. grout)—

Tiles needed (no wastage)—

Tiles needed (with wastage)—

Boxes to buy—

— tiles · — boxes

Always round boxes up — never down. Consider buying 1–2 extra boxes from the same batch for future repairs; dye lots vary between production runs.

How Many Tiles Do I Need?

The basic calculation divides the area you want to tile by the area of one tile. But real-world tiling is never quite that clean. Every cut tile wastes part of a whole tile, grout joints add millimetres between every tile, and rooms are rarely perfectly square. This calculator handles all of that automatically.

The key steps behind the maths:

Room area — length × width (or your entered total area), minus any deductions for cabinets or fixtures.
Tile area — the tile dimensions plus the grout joint on each side, converted from mm² to m².
Base tile count — net area ÷ tile area, rounded up to the nearest whole tile.
Wastage uplift — the base count multiplied by (1 + wastage %) to cover cuts, breakages and mistakes.
Boxes — final tile count divided by tiles per box, always rounded up.

The cost estimate multiplies the total tiles (with wastage) by your price per tile, giving a conservative upper estimate since you will likely have a few tiles left over.

Why Add Wastage for Tiles?

Even in a perfectly rectangular room, the perimeter tiles almost certainly need cutting. A 10% wastage buffer covers the cut offcuts, any tiles cracked during cutting or handling, and the slight discrepancy between the theoretical tile count and reality. For more complex layouts the wastage climbs quickly:

5% — very simple rooms, large tiles, minimal cuts. Acceptable for experienced tilers only.
10% — the industry standard for most residential floor and wall tiling jobs.
15% — L-shaped rooms, alcoves, many internal corners or lots of outlets to cut around.
20% — diagonal (45°) patterns, herringbone, or any pattern that runs at an angle to the walls.

Always source your tiles from a single batch (same dye lot) in one order. Tile colours can differ measurably between batches, and matching tiles months later is often impossible.

Frequently Asked Questions

For straightforward rectangular rooms with straight cuts, 10% wastage is standard. Allow 15% for rooms with many cuts — L-shapes, alcoves, lots of penetrations — and 20% for diagonal or herringbone patterns. It is always better to over-order slightly, as matching tiles from the same batch later can be difficult.

Break the room into rectangular sections, calculate each area separately, then add them together and enter the total in the Total Area field. Use the deductions field to subtract areas that won't be tiled, such as kitchen islands, large built-in fixtures or structural columns.

For rectified (precision-cut) porcelain tiles, joints as small as 1.5–2 mm are common. Standard ceramic tiles typically use a 3–5 mm joint. Larger format tiles (600 mm+) usually need at least 3 mm to allow for slight size variation. Natural stone often requires 5–8 mm. Always check your tile manufacturer's recommendation — some tiles are sold with spacer lugs built into the edges that determine the joint size for you.

A diagonal (45°) lay pattern creates significantly more cuts along all four walls, as every perimeter tile needs a mitred edge. Increase your wastage allowance to at least 15–20%. Enter your standard tile dimensions — the calculator handles the area maths correctly — then select 15% or 20% wastage from the dropdown to account for the additional cut pieces and higher breakage rate during angled cuts.