How to Calculate Tiles for Any Room
Working out how many tiles you need is one of the most important steps in any tiling project. Order too few and you risk delays waiting for replacement stock — or worse, discovering your tile has been discontinued. Order too many and you waste money on surplus boxes gathering dust in the garage. Our free tile calculator takes the guesswork out of this process by accounting for room dimensions, tile size, grout gaps, and a sensible wastage allowance.
The basic formula behind every tile calculation is straightforward: divide the total area you want to tile by the area of a single tile (including its share of the grout gap). The result is the minimum number of tiles for perfect, waste-free coverage — which, of course, never happens in practice. Every real-world tiling job involves cuts at edges, around obstacles, and the occasional breakage. That is why our calculator adds a configurable wastage percentage on top of the raw figure.
Step-by-Step: Measuring Your Room
Accurate measurement is the foundation of a good tile estimate. Here is how to get it right:
1. Gather Your Tools
You will need a retractable tape measure (at least 5 metres long), a notepad, and a pencil. A laser distance measurer is ideal for large rooms and can be purchased for as little as £20 from Screwfix or Toolstation. For irregular rooms, a piece of graph paper helps you sketch the layout.
2. Measure Length and Width
Measure the longest wall of the room and then the widest point perpendicular to it. Always measure at floor level rather than at worktop or eye height, as walls are rarely perfectly plumb. Take each measurement at least twice and use the larger figure — it is better to have a few spare tiles than to come up short.
3. Handle Irregular Shapes
For L-shaped rooms, alcoves, or bay windows, break the space into separate rectangles. Measure each rectangle individually and add the areas together. Our floor tile calculator includes an L-shape mode that does this automatically. For very complex shapes, consider laying out newspaper or cardboard and measuring the covered area.
4. Account for Obstacles
When tiling walls, you need to subtract the area of windows, doors, and any fixed fittings. Our wall tile calculator lets you add multiple deductions. Be precise — measure the window frame width and height, not just the glass. Include the door frame as well, not just the door itself.
Understanding Tile Sizes in the UK
Tile sizes in the UK are measured in millimetres. The most popular floor tile sizes are 300×300mm, 450×450mm, and 600×600mm. For walls, 300×600mm and the classic 200×100mm metro tile dominate. Large-format tiles (800×400mm and above) are increasingly popular for creating a seamless, modern look but require a flatter substrate and more careful handling.
| Tile Size (mm) | Tiles per m² | Common Use |
|---|---|---|
| 100 × 100 | ~94 | Mosaic features, splashbacks |
| 200 × 100 | ~48 | Metro/subway walls, kitchens |
| 300 × 300 | ~11 | Small bathroom floors |
| 330 × 330 | ~9 | Bathroom & utility floors |
| 450 × 450 | ~5 | Kitchen & hallway floors |
| 600 × 300 | ~5.4 | Bathroom walls, shower areas |
| 600 × 600 | ~2.8 | Living rooms, large kitchens |
| 800 × 400 | ~3 | Contemporary floors |
| 1200 × 600 | ~1.4 | Large open-plan spaces |
Wastage: How Much Extra Should You Order?
Wastage is the single most common source of frustration in tiling projects. The Tile Association (TTA) recommends a minimum of 10% wastage for straightforward rectangular rooms with a standard grid pattern. However, the actual figure depends on several factors:
- Room shape: Simple rectangles need 10%. Rooms with many alcoves, pipe runs, or curved walls may need 12–15%.
- Tile pattern: Diagonal (45°) layouts waste 10–15% more than straight lay. Herringbone patterns can waste 15–20% more due to the angle cuts at every edge.
- Tile size vs room size: Large tiles in small rooms produce more offcuts. A 600×600mm tile in a 1.5m-wide bathroom means almost half a tile wasted on every other row.
- Tile material: Natural stone and handmade tiles have a higher breakage rate. Budget 15% wastage for these materials.
- Your experience: First-time DIY tilers should add an extra 5% to whatever the guide suggests. Even experienced tilers occasionally snap a tile.
Grout Gaps: What Width to Use
The grout gap (or grout joint) affects both the appearance and the number of tiles you need. A wider grout gap means each tile effectively takes up a slightly larger area, so you need fractionally fewer tiles overall. British Standard BS 5385 provides guidance on minimum joint widths:
- Rectified tiles: 1.5–2mm (these are precision-cut with very consistent edges)
- Standard wall tiles: 2–3mm
- Standard floor tiles: 3–5mm
- Natural stone: 3–5mm (to allow for slight size variations)
- External/patio tiles: 5–10mm
Our calculator defaults to 3mm for floors and 2mm for walls, which matches the most common UK practice. You can adjust this to see how different grout widths affect your tile count.
How Many Boxes Should I Order?
Tiles are sold by the box in the UK, and each box covers a set number of square metres. The number of tiles per box varies by manufacturer and tile size. Typical examples include 6 tiles per box for 600×600mm, 10 tiles per box for 300×300mm, and 25 tiles per box for 200×100mm metro tiles. Our calculator rounds up to the nearest whole box, because retailers such as Topps Tiles, Wickes, and B&Q sell by the full box only. Always check the box coverage printed on the packaging and compare it to the calculator's output.
Tips for Accurate Tile Calculations
- Measure in metres — convert feet to metres by multiplying by 0.3048. Our calculator works in metric to match UK tile specifications.
- Double-check your room dimensions — measure at least twice, in different spots, and use the largest figure.
- Do not forget skirting areas — if you are tiling a floor up to the skirting, include the full wall-to-wall distance.
- Consider tile orientation — a 600×300mm tile laid landscape versus portrait can change the look and the number of cuts required.
- Check for batch consistency — order all tiles at once, from the same batch, to avoid colour variation.
- Plan your layout — a dry lay (placing tiles without adhesive) helps you see where cuts fall and whether you need to adjust the starting point to avoid thin slivers at the edges.
Frequently Asked Questions
The number of tiles per square metre depends on the tile size. For example, 300×300mm tiles give you approximately 11 tiles per m², 600×600mm tiles give about 3 tiles per m², and 100×100mm tiles give about 100 per m². Always add 10–15% for wastage from cuts and breakages.
For a standard straight-lay pattern, allow 10% wastage. For diagonal or herringbone patterns, allow 15–20%. For small rooms or rooms with many obstacles (pipes, corners), allow up to 15%. It is always better to order extra, as matching batches later can be difficult.
For floor tiles, a 3mm grout gap is standard in the UK. Larger format tiles (600×600mm and above) may use 2–3mm gaps. Rectified tiles can use gaps as small as 1.5–2mm. Natural stone typically needs 3–5mm. The British Standard BS 5385 recommends a minimum 2mm gap for wall tiles and 3mm for floors.
In 2026, UK tile prices range from £12–45/m² for ceramic, £20–70/m² for porcelain, and £40–120/m² for natural stone. Budget ranges at Wickes and B&Q start around £12/m², mid-range at Topps Tiles averages £25–40/m², and premium options from specialist suppliers can exceed £100/m².
Yes, always buy tiles from the same production batch. Tiles from different batches can have slight variations in colour, size, and shade even if they share the same product code. Check the batch number on the box. Order all your tiles at once, including wastage, to avoid batch mismatches.