How Many Tiles Do I Need? A Practical Calculation Guide
The core calculation for tile quantity is simple division — but getting an order that's actually right for your project means thinking about layout pattern, cuts, and how tile is packaged and sold. Here's how to go from room dimensions to a number you can confidently take to the store.
The basic calculation
Start by finding your area, then divide by the area of a single tile:
For example, a 4m × 3m room is 12 square meters. If you're using 60cm × 60cm tiles (0.36 square meters each):
Always round up to the next whole tile — you can't buy a third of a tile, and this number doesn't yet include any allowance for cuts or breakage.
Waste percentage by layout pattern
The 34 tiles above is the bare minimum for a perfectly simple layout with zero cuts — which essentially never happens in practice. How much extra to add depends largely on your layout pattern:
| Layout | Recommended waste |
|---|---|
| Simple grid, square/rectangular room | 10% |
| Diagonal or herringbone pattern | 15% |
| Irregular room shape, many corners/cuts | 15-20% |
For our 34-tile example with a 10% allowance, that comes to about 37.4, rounded up to 38 tiles. Diagonal layouts waste more material because most cut pieces along the edges can't be reused elsewhere, unlike a grid layout where offcuts from one row can sometimes be used to start the next.
Buying by the box
Tile is almost always sold by the box rather than individually, and box quantities vary significantly between products and manufacturers — some boxes hold 4 large tiles, others hold 10 or more smaller ones. Once you know your total tile count including waste, check the coverage area or tile count printed on the box and divide to find how many boxes to buy, rounding up to the nearest full box. It's normal for this final rounding to add a small amount of extra material beyond your waste percentage — that's a good thing, since leftover tiles are useful for future repairs.
Should you subtract doors and windows?
For wall tile, large openings such as doorways are usually subtracted from your total wall area before calculating quantity, since they represent meaningful unused space. For floor tile, small obstructions like cabinet toe-kicks or floor vents are often left in the calculation as-is — the area is small enough that it's easier to let the waste percentage absorb it than to calculate precise cutouts. There's no strict rule here; it mostly comes down to how much precision is worth the extra time for your project.
Grout lines and tile count
Grout joints take up a small amount of space between tiles, which can marginally affect tile count on larger jobs. For most residential rooms this effect is small enough to be covered by your waste percentage — see our tile grout gap guide for more on choosing a joint width.
Putting it together
The short version: calculate your area, divide by tile size, round up, then add a waste percentage based on your layout pattern before rounding up again to full boxes. If you'd rather not do this by hand, our tile calculator takes your room dimensions and tile size and handles the area, waste, and rounding for you.
FAQ
How do I calculate how many tiles I need for a room?
Divide the total floor or wall area by the area of a single tile, then round up. For a 12 square meter room with 0.36 square meter tiles (60x60cm), that's 12 divided by 0.36, which equals about 33.3, rounded up to 34 tiles before adding waste.
How much extra tile should I buy for waste?
For a simple grid layout in a square or rectangular room, 10% extra is typically enough. For diagonal, herringbone, or other complex patterns, or for rooms with lots of corners and cuts, 15-20% is safer.
Should I subtract doors and windows from my tile area?
For wall tile, large openings like doors are usually subtracted from the total area. Small openings or floor tile around fixtures are often left as-is and covered by the waste percentage instead, since the time saved rarely justifies the extra calculation.
Do grout lines change how many tiles I need?
Grout lines take up a small amount of space, which can slightly increase the number of tiles needed on large jobs. For most residential rooms, this difference is small enough to be covered by your waste percentage.