How it’s worked out
Counting rows and columns, with any part tile counted whole, is more honest than dividing the area by a tile’s area, which forgets that a cut tile’s offcut is often no use. A 3 × 2 m floor in 30 cm tiles with 3 mm gaps is 10 × 7 = 70 tiles, 77 with 10% extra.
Across = ⌈length ÷ (tile width + gap)⌉ Down = ⌈width ÷ (tile height + gap)⌉ Tiles = across × down, plus the extra %
Tiles per square metre
With a 3 mm grout gap, worked out by this calculator (the per-square-metre figure suits large areas; for small ones use the calculator):
| Tile size | Tiles per m² | With 10% extra |
|---|---|---|
| 10 × 10 cm | 94.3 | 104 |
| 20 × 20 cm | 24.3 | 27 |
| 30 × 30 cm | 10.9 | 12 |
| 60 × 30 cm | 5.5 | 7 |
| 60 × 60 cm | 2.8 | 4 |
| 120 × 60 cm | 1.4 | 2 |
How much extra?
- 10% for a straight layout in an ordinary room.
- 15% for a diagonal or herringbone layout, small rooms with many cuts, or fragile tiles.
- Keep a few spare: matching a tile years later is hard.
How to read the result
- Tiles to buy: every cut tile counted whole, plus the extra.
- Boxes and cost: once you type the box size and price.
- Tiles laid: before the extra, so you can see what it adds.
Common mistakes
- Dividing the area by a tile’s area: it undercounts the cut tiles at the edges.
- Forgetting the grout gap with small tiles.
- Buying exactly enough: tiles from a later batch rarely match.
How to use it
- Type the length and width of the floor or wall.
- Type the tile size and grout gap.
- Choose the extra for cuts and breakages; add the tiles in a box and price to get boxes and cost.
Questions
How many tiles do I need for 1 m²?
About 10.9 tiles of 30 × 30 cm with 3 mm gaps, or 2.8 of 60 × 60 cm, before extra.
Should I leave out a bath or kitchen units?
Yes: measure only where tiles go, and add separate areas together.
Why buy all the tiles at once?
Shades vary between batches, so tiles bought later may not match.
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