Updated July 8, 2026
Start with the room, not the tile
Tile shopping usually starts backward, at the showroom, picking a pattern before anyone has measured the space it needs to cover. Flip that order. Measure the room first, decide the layout (straight or diagonal), and only then price tile against a number you actually trust. To calculate tiles needed: find the room's square footage (length times width), divide by the square footage of one tile, then add 10 percent for waste, 15 percent for diagonal or pattern layouts. For a 120-square-foot bathroom with 12x12 tiles (1 sq ft each), that is 120 tiles plus 12 for waste, 132 tiles minimum.
Tile size to square footage conversion
| Tile size | Sq ft per tile | Tiles per 100 sq ft (before waste) |
|---|---|---|
| 6 x 6 in | 0.25 sq ft | 400 |
| 12 x 12 in | 1.00 sq ft | 100 |
| 12 x 24 in | 2.00 sq ft | 50 |
| 18 x 18 in | 2.25 sq ft | 44 |
| 24 x 24 in | 4.00 sq ft | 25 |
| 3 x 6 in subway | 0.125 sq ft | 800 |
The order-quantity formula, step by step
- Measure the area to tile: length times width in feet equals square feet.
- Find the tile's square footage: multiply tile length by tile width in feet. A 12x12 tile is 1 x 1, or 1 sq ft.
- Divide area by tile size: 120 sq ft divided by 1 sq ft equals 120 tiles.
- Add 10 percent waste: 120 times 1.10 equals 132 tiles.
- Round up to the nearest box quantity your supplier sells.
Why the waste buffer is worth the extra cost
A bigger tile wastes more per cut than it looks like it should. Add 15 percent if the layout is diagonal, the room has a lot of corners or cut-outs, or the tile itself is large (24x24 and up), since an edge cut on a big tile throws away more material than the same cut on a small one. On a 120-square-foot bathroom at $4 a square foot, the jump from 10 to 15 percent waste is about $24, cheap insurance against a mid-project trip back to the store for a tile that may already be sold out of that dye lot. Use our tile calculator to run your exact layout with grout joint width included.
Grout, spacers and the rest of the shopping list
The tile count above does not include grout. For a standard 1/8 inch joint, the spacing barely changes the tile count but does change how much grout to buy, and coverage varies by tile size and joint width, so check the bag label rather than guessing. Spacers come in packs and get consumed one per intersection, so budget a pack per 50 to 100 square feet as a starting point, and add both line items to the same shopping trip as the tile itself.
Backsplashes and multi-room jobs
Wall and backsplash tile is usually sold by the square foot rather than the box. Measure the backsplash area (length times the height between counter and upper cabinets), subtract outlet and switch cutouts at roughly 0.5 sq ft each, and add 10 percent. Wall tile chips more easily than floor tile, so lean toward 12 to 15 percent waste there. If a kitchen backsplash and a bathroom floor are happening in the same renovation, price them as two separate orders since the waste factor and tile size rarely match between the two.
Run your own layout
Enter your room and tile size to get an exact order count.