Quick answer: To measure for tiles, work out the area to be tiled in square metres (length × width for floors, width × height for walls), subtract doors, windows and fittings, then add 10% for cuts and breakages, or 15% for diagonal or herringbone layouts. Divide by the coverage per box and round up to whole boxes.
Tiling quantities trip people up because walls have openings, floors have awkward edges, and tiles come in boxes rather than by the square metre. This guide covers floors and walls, tiles per square metre for common UK sizes, the grout joint widths in the British Standard, and how to set out so you avoid thin cuts. It sits within the home measuring guides.
What do you need to measure for tiles?
- A metric tape measure or laser measure
- A spirit level and pencil, for marking tile heights on walls
- A sketch of each wall or floor with doors, windows, the bath, basin and any boxing-in marked
- The tile size and the coverage per box from the product details
How do you measure a floor for tiles?
Multiply the length by the width of the floor in metres, add any recesses as separate rectangles, then add your waste allowance. Floors are usually the simpler job, because there are no windows to subtract.
- Measure wall to wall at floor level in two directions, checking both ends of each wall.
- Split L-shapes and recesses into rectangles and add them together, as shown in the guide to measuring a room in square metres.
- Subtract fixed items that will not be tiled under, such as kitchen base units or a fitted bath, if they are staying in place.
- Add the waste allowance for your layout (see below) and divide by the box coverage.
Worked example: a kitchen floor 3.2 m × 2.5 m is 8.0 m². With 10% extra that is 8.8 m². Each 600 × 600 mm tile covers 0.36 m², so 8.8 ÷ 0.36 = 24.4, meaning 25 tiles. Laid diagonally with 15% extra, it becomes 9.2 m² and 26 tiles.
How do you measure a wall for tiles?
Multiply the width of each wall by the height you will tile, subtract windows, doors and anything in front of the wall, then add back window reveals. Measure each wall separately and add them up at the end.
- Height: measure from the floor, worktop or bath rim to where the tiling will stop, whether that is the ceiling, a set height or the top of a splashback.
- Windows and doors: width × height of each opening, subtracted from the wall.
- Reveals: if the sides and top of a window recess will be tiled, add their area (depth × length of each side).
- Boxing-in: pipe boxing adds area on its front and sides; measure each face.
For the wall in the diagram, 4.70 m² plus 10% is 5.17 m². Using 300 × 600 mm tiles (0.18 m² each), 5.17 ÷ 0.18 = 28.7, so you need 29 tiles. If you are papering rather than tiling some walls, the guide on measuring for wallpaper uses the same wall measurements.
Kitchen splashbacks and shower enclosures follow the same rule on a smaller scale. For a splashback, measure the length of each worktop run and the height from the worktop to the underside of the wall cupboards or to your chosen finishing line, then subtract the cooker hood or any window. For a shower, measure each tiled wall from the tray to the finished height, and remember that a small area with lots of cuts justifies the higher waste allowance.
Tile calculator
m² tile × mm + %=How many tiles are in a square metre?
Divide 1 by the area of one tile in square metres: a 300 × 300 mm tile is 0.09 m², so there are about 11.1 tiles per m². The figures below ignore grout joints, which slightly reduce the number needed; your waste allowance more than covers the difference.
| Tile size (mm) | Approx. inches | Area per tile | Tiles per m² |
|---|---|---|---|
| 75 × 150 (metro) | 3 × 6 in | 0.01125 m² | 88.9 |
| 100 × 100 | 4 × 4 in | 0.01 m² | 100 |
| 150 × 150 | 6 × 6 in | 0.0225 m² | 44.4 |
| 200 × 200 | 8 × 8 in | 0.04 m² | 25 |
| 250 × 400 | 10 × 16 in | 0.10 m² | 10 |
| 300 × 300 | 12 × 12 in | 0.09 m² | 11.1 |
| 300 × 600 | 12 × 24 in | 0.18 m² | 5.56 |
| 600 × 600 | 24 × 24 in | 0.36 m² | 2.78 |
| 600 × 1200 | 24 × 47 in | 0.72 m² | 1.39 |
Tiles are sold by the box, and each box lists its coverage in m². Divide your total (including waste) by the box coverage and round up. Buy every box from the same batch, shown as a batch or shade code on the label, because colour can vary slightly between production runs.
How much extra should you allow for tile wastage?
Allow 10% for a straight layout and 15% for diagonal, brick bond or herringbone patterns. Topps Tiles' calculator adds 10% for cuts and wastage, and Tile Mountain recommends 15% for diagonal, brick bond and herringbone layouts because they produce more offcuts.
| Layout or situation | Typical extra to allow |
|---|---|
| Straight lay (grid) | 10% |
| Diagonal, brick bond or herringbone | 15% |
| Large format (600 × 600 mm and above) in a room under 5 m² | 15 to 20% |
Keeping a few spare tiles after the job is worthwhile too. If one cracks in a few years, a matching replacement from the same batch may be impossible to find.
How wide should grout joints be?
The British Standard for tiling, BS 5385, sets minimum joint widths of 2 mm for most wall tiles and 3 mm for floor tiles. These are minimums; rectified porcelain is often laid with narrow joints, while rustic or handmade tiles need wider ones.
| Where | Tile size | Minimum joint width |
|---|---|---|
| Walls (BS 5385-1) | Under 0.1 m² and no side over 600 mm | 2 mm |
| Walls (BS 5385-1) | 0.1 to 1 m², no side over 1,200 mm | 3 mm |
| Floors (BS 5385-3) | Ceramic tiles | 3 mm, and no wider than the tile is thick |
How do you set out tiles to avoid thin cuts?
Start from the centre of the floor or wall, not from one edge, and adjust by half a tile if the edge cuts come out too thin. Balanced cuts on opposite sides look deliberate, while a full tile on one side and a sliver on the other draws the eye.
To check a layout before fixing, make a gauge stick: a straight batten marked with tile widths plus joints. Hold it against the wall or floor from the centre line to see where the last full tile lands. Reading those marks accurately is easier with a good tape; the guide to reading a tape measure covers the millimetre scale.
Common mistakes to avoid
- Measuring the room instead of the tiled area. Walls are rarely tiled to the ceiling everywhere, so measure the actual tiled height on each wall.
- Forgetting reveals and boxing. They add surprising area in small bathrooms.
- Mixing up tiles and boxes. Check whether a price or quantity is per tile, per m² or per box.
- Ordering without a margin. Running short mid-job risks a different batch with a visible shade difference.
- Treating different floor finishes alike. Tiles are counted individually and laid with joints; laminate is ordered by the pack with an expansion gap, as explained in how to measure for laminate flooring.
Frequently asked questions
How do I work out how many tiles I need?
Measure the area to be tiled in square metres, add 10% (15% for diagonal or herringbone), and divide by the area of one tile or by the box coverage. Round up to a whole number.
How many 600 x 600 tiles are in a square metre?
About 2.78. Each 600 × 600 mm tile covers 0.36 m², and 1 ÷ 0.36 = 2.78.
Should I subtract windows when measuring for wall tiles?
Yes. Subtract the width × height of each window and door, then add back the reveals if the sides and top of the window recess are being tiled.
What is the minimum grout gap for floor tiles in the UK?
BS 5385-3 gives a minimum of 3 mm for ceramic floor tiles, and says the joint should not be wider than the tile is thick.
How many spare tiles should I keep?
Keep any leftover full tiles from the same batch. A handful is enough to replace a cracked tile later without a mismatch.
Sources
- The Tile Association: Tiling Guide (BS 5385 joint widths)
- Topps Tiles: Tile calculator (10% wastage allowance)
- Tile Mountain: How many tiles do I need? (pattern and large-format allowances, deducting openings)
- BSI, publisher of BS 5385 Wall and floor tiling
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- How to Measure a Mattress (UK Guide with Size Chart)
- UK Bed Sizes in CM: Single, Double, King and Super King
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