How Many Tiles Do I Need? The Waste Rule Nobody Follows
Published 2026 · 4 min read
The easiest way to run out of tiles mid-project is to order exactly what the math says and skip the waste allowance. The math is simple — the allowance is where every beginner goes wrong.
The basic calculation
Measure your room's area (length — width), then divide by the area of one tile. A 12 — 10 ft room is 120 square feet; 12-inch tiles cover 1 square foot each, so you need 120 tiles.
Why you add 10%
- Cuts: edges, corners, doorways and fixtures need partial tiles.
- Breakage: tiles crack during cutting or carrying.
- Repairs later: a cracked tile two years in is painful if you can't match the batch.
10% covers these for a straight lay. Diagonal patterns and busy rooms push that toward 15?20%.
The trap: dye lots
Tiles are sold in boxes, so round up to whole boxes. Never rely on "buying a few more later" — dye lots differ between batches, so a later box can look visibly different.
Run the numbers
Use the tile calculator — enter room size, tile size and your waste allowance, and it rounds up to the exact tiles to buy.
For patterned, large-format or diagonal layouts, bump the allowance toward 15% rather than 10%, because every wall and doorway produces angled cuts that waste more than a straight lay. And if the tile is being discontinued or is a special order, buy the spare box now - matching a discontinued tile later can mean replacing a whole floor instead of one damaged piece.