How to calculate tiles
Divide the area you're covering by the area of a single tile, then add a waste allowance and round up. Convert the tile size to square feet by multiplying its width and height in inches and dividing by 144:
Tiles = (Floor area ÷ Tile area) × (1 + waste %)
A 12 ft × 10 ft floor is 120 square feet. With 12 × 12-inch tiles, each tile covers 1 square foot, so you need 120 tiles plus a 10% allowance — 132 tiles.
How much waste to add
- Straight / grid lay: 10% is the standard allowance.
- Diagonal or herringbone: 15% — angled cuts waste more.
- Lots of cuts (around cabinets, fixtures): lean toward 15%.
Buy every tile in one order so they share a dye lot — colors drift between batches, and matching later is difficult. Keep a few spares after the job for future repairs.
Boxes and cost
Tile is usually sold by the box. Enter the tiles per box (printed on the packaging, sometimes as a coverage in square feet) to see how many boxes to buy, and add a price per tile for a quick material estimate.
Frequently asked questions
How do I calculate how many tiles I need?
Find the area to be tiled (length × width) and the area of one tile (tile width × tile height ÷ 144 for square feet), then divide the room area by the tile area and round up. Add 10% for cuts and breakage. A 120 sq ft floor with 12 × 12-inch tiles (1 sq ft each) needs 120 tiles plus waste, so about 132.
How much extra tile should I buy for waste?
Add 10% for a standard straight or grid layout, and 15% for diagonal, herringbone, or rooms with lots of cuts around fixtures. Buy it all at once so the tiles come from the same batch — dye lots vary, and matching later is hard.
How many tiles come in a box?
It varies by tile size and brand, so check the box — common counts are 6 to 12 tiles, often listed as the square footage the box covers. Enter the tiles per box in the calculator to get the number of boxes to order.
Do I include the grout lines in the calculation?
For ordering purposes you can ignore grout lines — using the nominal tile size slightly overestimates coverage, which conveniently builds in a small buffer. The waste allowance covers cuts and the occasional broken tile.
Disclaimer: Results are estimates for planning. Confirm the exact tile size and box coverage with your supplier, and always buy a little extra for cuts and future repairs.