Calculate the exact number of tiles for your floor or wall tiling project. Enter your room dimensions, tile size, grout joint width, and wastage to get an accurate tile count instantly.
Tiling is one of the most rewarding DIY projects you can tackle at home. Whether you are laying floor tiles in a kitchen, bathroom or hallway, or tiling a shower enclosure or splashback, the end result dramatically transforms a room. Getting your tile calculations right before you buy is essential — too few tiles and you face a second trip to the shop hoping the batch is still available, too many and you have wasted money. This guide covers everything you need to know about calculating tile quantities, choosing the right tile size, grout joints, adhesive, and installation techniques.
The starting point for any tile calculation is the area to be tiled. For a rectangular room, this is simply length multiplied by width. However, the number of tiles you actually need is not simply the area divided by the tile area — you must account for the grout joint between each tile, which effectively reduces the coverage of each tile slightly, and you must add a wastage allowance for cuts, breakages and mistakes.
The effective tile size (including one grout joint on two sides) is calculated as: (tile length + grout joint) × (tile width + grout joint). For a 300x300mm tile with a 3mm grout joint, the effective tile size is 303mm × 303mm = 0.0918 m², which means approximately 10.9 tiles per m² rather than exactly 11.1 tiles per m² from the raw tile area.
| Tile Size | Tiles per m² (2mm joint) | Tiles per m² (3mm joint) | Tiles per m² (5mm joint) |
|---|---|---|---|
| 600 × 600 mm | 2.77 | 2.75 | 2.72 |
| 600 × 300 mm | 5.55 | 5.51 | 5.44 |
| 450 × 450 mm | 4.92 | 4.88 | 4.82 |
| 300 × 300 mm | 10.92 | 10.78 | 10.52 |
| 250 × 500 mm | 7.94 | 7.86 | 7.71 |
| 200 × 200 mm | 24.51 | 24.01 | 23.08 |
| 150 × 150 mm | 43.30 | 41.99 | 39.68 |
| 100 × 100 mm | 96.12 | 92.34 | 85.73 |
Tile size has a significant impact on how a room feels. The current trend in UK homes is toward large-format tiles (600×600mm and above), which create a sleek, modern appearance, reduce visible grout lines, and make smaller rooms feel more open and spacious. However, they are heavier, require a more perfectly flat substrate, and can be more difficult to cut and handle as a DIY project.
The grout joint serves both a practical and aesthetic purpose. Practically, it accommodates slight size variations between individual tiles (all tiles have a manufacturing tolerance), allows for thermal expansion and prevents cracking, and provides grip for the grouting that locks the installation together. Aesthetically, it defines the pattern of the tiles and can be used to create a near-seamless look (with a 2mm rectified joint) or a more traditional appearance (with a 5-10mm joint).
| Joint Width | Best For | Grout Type |
|---|---|---|
| 1–2 mm | Rectified porcelain tiles, minimal-grout contemporary look | Unsanded (fine-grain) grout |
| 3 mm | Standard ceramic and porcelain floor and wall tiles | Unsanded or fine-sanded grout |
| 5 mm | Natural stone, handmade ceramic, tiles with size variation | Sanded grout |
| 8–10 mm | Quarry tiles, traditional terracotta, external paving | Sanded or coarse grout, mortar |
The correct wastage allowance is one of the most important factors in ordering tiles. Too little and you face a stressful last-minute order, often from a different batch. Too much and you waste money. Here is the guidance used by professional tilers in the UK:
Estimating grout quantities can be tricky, but the following formula provides a reliable estimate. The weight of grout in kilograms per square metre is approximately:
Grout (kg/m²) = (tile length + tile width) ÷ (tile length × tile width) × joint width × tile depth × grout density
For practical purposes, here are approximate grout requirements for common tile and joint combinations:
| Tile Size | Joint Width | Approx. Grout (kg/m²) | 5kg bag covers |
|---|---|---|---|
| 600 × 600 mm | 3 mm | 0.28 kg | ~18 m² |
| 300 × 600 mm | 3 mm | 0.42 kg | ~12 m² |
| 300 × 300 mm | 3 mm | 0.56 kg | ~9 m² |
| 200 × 200 mm | 3 mm | 0.84 kg | ~6 m² |
| 150 × 150 mm | 3 mm | 1.12 kg | ~4.5 m² |
The pattern in which you lay your tiles affects both the final appearance and the wastage. These are the most common patterns used in UK homes:
Not all tiles are suitable for both floors and walls, and the installation methods differ significantly:
Surface preparation is the most critical factor in a successful tiling project. Even the best tiles and adhesive will fail if the substrate is not properly prepared:
| Tile Type | Typical Cost per m² | Notes |
|---|---|---|
| Budget ceramic floor tiles | £8–£15 | B&Q, Wickes, Topps Tiles value range |
| Mid-range porcelain floor tiles | £20–£40 | 600×600mm, wood-effect and stone-effect |
| Premium large-format porcelain | £45–£80 | 600×1200mm, marble-effect slabs |
| Ceramic wall tiles | £10–£25 | Bathroom and kitchen wall tiles |
| Metro / subway tiles | £12–£30 | 75×300mm, very popular kitchen splashback |
| Natural stone (slate, travertine) | £30–£80+ | Requires sealing. Higher wastage for cutting. |
| Tile adhesive (20kg bag) | £8–£15 | Covers 4-5 m² at standard thickness |
| Grout (5kg bag) | £5–£12 | Coverage varies by tile/joint size — see table above |