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Tile Calculator

Work out how many tiles or boxes of flooring to buy for a floor or wall, with the waste you choose.

Area lengthArea widthThe floor or wallGrout jointTile lengthTile widthClose-up
Key The area to cover, and one tile with its grout joint.
Units
Work out by
Area to cover

Add a rectangle for each part of an L-shaped or split room.

Common tile sizes. 300, 450 and 600 mm squares, and 300 x 600 mm rectangles. Use the size printed on the box. Editorial rule of thumb.
mm
mm
mm
%
Area12 m²
Tiles with no waste133.3
Tiles to buy, with waste147 tiles
Area the tiles cover13.23 m²

4 × 3 m = 12 m². 12 m² ÷ one 300 × 300 mm tile = 133.33 tiles; with 10% waste = 146.67, rounded up to 147.

Diagonal or patterned layouts need more waste, commonly 15%. Grout and adhesive are not included.

Fig. 1 Tiles for your floor or wall.

Every formula is tested against worked examples. How we check

WasteTilesArea
5%140 tiles12.6 m²
10%147 tiles13.23 m²
15%154 tiles13.86 m²

Fig. 2 The same floor at common waste allowances.

Last checked 10/11/2026. Defaults are editorial rules of thumb; each one is explained in the guide below.

Guide

How the amount is worked out

Each tile covers its own size plus half a grout joint on each side. Tiles = area ÷ (tile length + joint) × (tile width + joint). Add waste, then round up to whole tiles, then to whole boxes.

Example. A 4 m² bathroom floor of 300 × 300 mm tiles with no grout joint is 44.4 tiles. With 10% waste that is 48.9, so 49 tiles.

How much waste?

10% is a common starting point for straight layouts. Diagonal or patterned layouts, rooms with many corners and small tiles need more; 15% is common for diagonal layouts. Keep a few spares from the same batch for future repairs, because batches vary.

Flooring by box

Plank flooring is sold by the box, and each box states its coverage in square metres. Switch to "by box coverage" and enter the figure from the box. Round up to whole boxes.

What is not included

Grout, adhesive and underlay depend on tile size, joint width and trowel notch, and there is no single defensible coverage figure, so this calculator leaves them out. Check the bag or the manufacturer’s coverage table.

Common questions

How many tiles for a 4 m2 bathroom floor?

With 300 x 300 mm tiles and no joint, 44.4 tiles; with 10% waste, 49 tiles.

Should I measure the room twice?

Yes. Add rooms made of several rectangles one after another and double-check measurements before ordering.

Does the grout joint matter?

A little. A 3 mm joint on 300 mm tiles makes each tile cover about 2% more, which can save a tile or two.

Do wet-area tiles need anything extra?

Waterproofing and falls in wet areas are regulated and are not covered here. Ask a licensed tradesperson.

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