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.