How the tile calculator works
To work out how many tiles you need, the calculator divides the area you're tiling by the area each tile covers once you include its share of the grout joint, then adds a percentage for cuts and breakages and rounds up:
area per tile = (tile width + grout gap) × (tile height + grout gap)
tiles = area to tile ÷ area per tile × (1 + wastage %), rounded up
boxes = tiles ÷ tiles per box, rounded up
Tile sizes in the UK are almost always given in millimetres (such as 300 × 600mm or 600 × 600mm), so enter them in mm. The wall or floor size goes in metres.
How to measure for tiles
- Walls: measure the width and the height you're tiling to. For a half-tiled bathroom, that might be 1.2m high rather than floor to ceiling.
- Floors: measure length and width. Split L-shaped rooms into rectangles and work out each one, or add the areas together and enter them as a single width with a height of 1.
- Take off what you won't tile, such as a window, door or the side of a bath, in the "areas not tiled" box.
- Measure each wall separately if they're different heights, then add the tiles together.
Choosing a grout gap and wastage
Most ceramic wall tiles use a 2 to 3mm joint. Floor tiles and large porcelain tiles typically use 3 to 5mm, and rustic or handmade tiles can need more. A wider gap means each tile covers slightly more area, so you need a few fewer tiles.
| Job | Wastage to add |
|---|---|
| Simple wall or floor, straight grid | 10% |
| Brick bond or lots of cuts around pipes and sockets | 12 to 15% |
| Diagonal or herringbone pattern | 15 to 20% |
| Large-format tiles (600mm and up) | 10 to 15% |
Keep a few spare tiles after the job. If one cracks later, finding a matching batch can be impossible.
Worked example: a 3m × 2.4m bathroom wall
- Area to tile: 3 × 2.4 = 7.2m²
- Each 300 × 600mm tile with a 3mm grout gap covers 303 × 603mm = 0.1827m²
- Tiles to cover the area: 7.2 ÷ 0.1827 = 39.4
- Add 10% wastage: 39.4 × 1.1 = 43.3, rounded up to 44 tiles
- At 6 tiles per box, you need 8 boxes (7.3 rounded up). At £25 a box that's £200.
A 4m × 3m kitchen floor in 600 × 600mm porcelain with 3mm joints and 15% wastage needs 38 tiles. In boxes of 4, that's 10 boxes.
How many tiles in a square metre?
With a 3mm grout joint, roughly:
| Tile size | Tiles per m² (no wastage) |
|---|---|
| 100 × 100mm | 94.3 |
| 200 × 250mm | 19.5 |
| 300 × 300mm | 10.9 |
| 300 × 600mm | 5.5 |
| 600 × 600mm | 2.8 |
Tips before you buy
- Check the batch or shade number on every box. Colours can vary between production runs.
- Box sizes vary. Some retailers sell by the m² rather than by the box, so check how many tiles a box holds and enter it above.
- Buy adhesive and grout to suit the tile. Large porcelain tiles usually need a flexible adhesive and a notched trowel with deeper teeth. Coverage is printed on the bag.
- Think about trims for external corners and edges, and measure the total length you need.
Laying laminate or vinyl instead? Try the flooring calculator. For the walls you aren't tiling, the paint calculator works out the litres of emulsion, and the concrete calculator helps with a new base for a patio.
Frequently asked questions
How many tiles do I need for 1 square metre?
It depends on the tile size. With a 3mm grout joint you need about 11 tiles of 300 × 300mm, 5.5 tiles of 300 × 600mm or 2.8 tiles of 600 × 600mm per m², before adding 10% for cuts.
How much extra tile should I buy?
Add 10% for a straightforward job and 15% or more for diagonal layouts, herringbone or rooms with lots of cuts. It's better to have a few spare tiles than to run short and find the batch has sold out.
Should I include the grout gap when working out tiles?
Yes, especially for small tiles. The joint adds a little to the area each tile covers, so with 100 × 100mm tiles and a 3mm gap you need about 94 tiles per m² rather than 100.
How many tiles do I need for a splashback?
A typical splashback 3m long and 0.6m high is 1.8m². With 100 × 200mm metro tiles and 2mm joints, that's about 88 tiles before wastage (87.4 rounded up), or 97 with 10% extra.
What size grout gap should I use?
Most ceramic wall tiles use a 2 to 3mm joint, while floor tiles and large porcelain tiles usually use 3 to 5mm. Check the tile manufacturer's guidance, as rectified tiles can take narrower joints.
Last reviewed October 2026 using 2026/27 figures. This calculator gives an estimate for guidance only.