Show the formula and working
This bathroom tile calculator works out how many wall tiles and floor tiles you need for a bathroom, and how many boxes to buy, for homeowners and fitters in the UK, Ireland and the rest of Europe. It measures all four walls from the room size and tiling height, takes off the door, window and areas hidden by the bath, and handles different tile sizes for the walls and the floor.
Quick answer: A bathroom tile calculator works out the wall area as the room perimeter times the tiling height, minus untiled areas, then divides by the tile size and adds 10%. A 2.5 m by 2 m bathroom tiled to 2.4 m with 3.5 m² untiled needs 110 tiles of 600 x 300 mm.
What Is a Bathroom Tile Calculator?
A bathroom tile calculator is a tool that estimates the number of wall and floor tiles needed to tile a bathroom, including an allowance for cuts and breakages. In plain words: wall area equals 2 x (length + width) x tiling height, minus the door, window and any wall hidden behind the bath or units. Tiles needed equals that area divided by the area of one tile plus its grout joint, increased by the waste percentage and rounded up. The floor works the same way, using length x width minus the area under the bath or shower tray.
Adding the grout joint to each tile edge matters for small tiles. A 100 mm tile with a 2 mm joint covers 102 mm, so about 4% fewer tiles are needed than a calculation without joints suggests. For a 600 mm tile the difference is tiny. The grout article explains joint materials and why wider joints suit uneven or handmade tiles.
How Do You Use the Bathroom Tile Calculator?
- Enter the Room length, Room width and Wall tiling height. Use about 1.2 m for half height tiling.
- Enter the Wall area not tiled: the door, window and wall hidden behind the bath or fitted units.
- Enter the Wall tile length, Wall tile width and Wall tiles per box.
- Leave Tile the floor too ticked, then enter the Floor area not tiled, the Floor tile length, Floor tile width and Floor tiles per box.
- Set the Grout joint width and the Extra for cuts and breakages.
- Read the tiles and boxes needed, then open “Show the formula and working” to see each step.
How Many Tiles Do I Need for a Small Bathroom?
A small 2.5 m by 2 m bathroom tiled floor to ceiling has about 18 m² of wall to tile once the door and bath are taken off, plus about 4 m² of floor. That is about 110 wall tiles of 600 x 300 mm and 46 floor tiles of 300 x 300 mm with 10% extra. Half height tiling at 1.2 m roughly halves the wall figure. For a single wall or floor, the general tile calculator is quicker.
How Much Extra Tile Should I Buy?
Buy about 10% extra for a straight layout and about 15% for diagonal, herringbone or large format tiles. Bathrooms have many cuts around the bath, basin, pipes and window reveals, and a few tiles break during cutting. Keep spare tiles from the same batch after the job, because the colour of fired ceramic and porcelain tiles can vary between batches and a cracked tile years later is hard to match.
Should I Tile Behind the Bath?
You do not usually need to tile the wall hidden behind the bath below the rim, so measure it and include it in the wall area not tiled. Tile at least one row below the top of the bath so water cannot run behind it, and seal the joint between the bath and tiles with flexible silicone sealant. Shower areas need a waterproof base such as cement backer board or a tanking system, which the tile backer board calculator helps you size.
Tiles per Square Metre by Size
With a 2 mm grout joint. The last column adds 10% for cuts and breakages.
| Tile size | Tiles per m² | Tiles per m² with 10% extra |
|---|---|---|
| 100 x 100 mm | 96.1 | 105.7 |
| 150 x 150 mm | 43.3 | 47.6 |
| 200 x 200 mm | 24.5 | 27.0 |
| 250 x 400 mm | 9.9 | 10.9 |
| 300 x 300 mm | 11.0 | 12.1 |
| 300 x 600 mm | 5.5 | 6.1 |
| 600 x 600 mm | 2.8 | 3.0 |
| 600 x 1,200 mm | 1.4 | 1.5 |
Worked Example: A 2.5 m by 2 m Family Bathroom
Example: a bathroom is 2.5 m by 2 m and tiled to 2.4 m high. The walls measure 2 x (2.5 + 2) x 2.4 = 21.6 m². Taking off 3.5 m² for the door, window and the wall behind the bath leaves 18.1 m². Each 600 x 300 mm tile with a 2 mm joint covers 0.602 x 0.302 = 0.1818 m², so the walls need 99.6 tiles, or 110 with 10% extra, which is 14 boxes of 8.
The floor is 2.5 x 2 = 5 m², minus 1.2 m² under the bath, leaving 3.8 m². Each 300 x 300 mm tile covers 0.302 x 0.302 = 0.0912 m², so the floor needs 41.7 tiles, or 46 with 10% extra, which is 5 boxes of 11. These are the default inputs, so the calculator shows the same result. Work out grout and adhesive for the same 21.9 m² with the grout calculator and the tile adhesive calculator.
Bathroom Tile Calculator FAQs
How do I measure a bathroom for tiles?
Measure the length and width of the room at floor level and the height you will tile to. Then measure the door, window and any wall hidden behind the bath, shower tray or fitted units, multiply each width by its height, and add them together as the untiled area.
Can I use wall tiles on a bathroom floor?
Usually not. Wall tiles are often thinner and softer and can crack under foot traffic, and many are slippery when wet. Use tiles the maker rates for floors, and choose a slip resistant finish for a bathroom, where floors are often wet.
How many tiles are in a box?
It depends on the size and brand. Boxes of 600 x 300 mm tiles often hold 8 tiles, about 1.44 m², and boxes of 300 x 300 mm tiles often hold 11, about 0.99 m². Check the label and enter the real number, as the defaults are only examples.
Do large tiles make a small bathroom look bigger?
Many people find that large tiles with thin, matching grout lines make a small bathroom look calmer and larger, because there are fewer lines. They need a very flat wall or floor and more care with cuts, so allow 15% extra.
Should I tile the whole bathroom or just the wet areas?
Tiling only the splash zones, around the bath, shower and basin, saves money and tiles, and the remaining walls can be painted with bathroom paint. Full height tiling is easier to clean and better for showers over baths. Enter your chosen height in Wall tiling height.
Can I tile over old bathroom tiles?
Sometimes, if the old tiles are firmly fixed, flat and clean and the wall can take the extra weight. Many fitters prefer removing them for a sound base, especially behind showers. Check the adhesive maker’s guidance before tiling over existing tiles.
Checked October 2026. Sources: Tile (Wikipedia), Grout (Wikipedia).