Quick answer: Divide the area by one tile's coverage (a 12×12-in tile = 1 sq ft) and add 10% for cuts — 15% for diagonal or herringbone. Buy from one lot number for color consistency.
Calculate exact tiles and boxes needed. Accounts for complex patterns and cabinet deductions.
Diagonal and herringbone layouts use the higher waste factors above for a reason. See the real dollar breakdown in our Tile Pattern Waste Guide.
Tile boxes are sold by total square footage, not piece count, because tile sizes vary so much — a 12x12" box might hold 10 tiles while a 6x6" box of the same coverage holds 40. Always check the box label for "sq ft per box" or "pieces per box" rather than assuming. If you only know the piece count, multiply tile length × width (in feet) × pieces per box to get the coverage.
Hexagon, penny round, and other non-rectangular tiles waste more material at room edges because their angled sides don't align with straight walls. Budget 15–20% waste for hexagon floor tile and up to 20% for intricate mosaic patterns, even though the tiles themselves are often sold pre-mounted on mesh sheets that simplify installation.
Order 10% extra for a standard grid layout, 15% for diagonal or offset patterns, and 20% for herringbone or other complex layouts, since those patterns create more angled cuts and discarded off-cuts.
Take your total room area, subtract any islands or cabinets, add your waste percentage, then divide by the square footage per box (printed on the box) and round up to the next full box.
Yes. Buy at least one extra box beyond your waste-adjusted total and store it. Tile dye lots change between production runs, so matching a broken tile years later is often impossible without leftover stock.
As a rough rule, a 25 lb bag of sanded grout covers roughly 80–100 sq ft of standard 12x12" tile with 1/8" grout lines. Larger tiles need less grout per square foot; smaller mosaic or subway tile needs more due to the higher ratio of grout line length to tile area.
A 1/4" x 3/8" square-notch trowel is standard for 12x12" floor tile. Larger format tile (16"+) typically needs a 1/2" notch trowel to maintain full mortar coverage under the tile.
Last reviewed August 2026 · how we source these figures
For 12 x 12 in tile at 15% waste (standard offset), with 10 sq ft per box. One tile per square foot before waste.
| Room | Area | 12x12 tiles @ 15% waste | Boxes (10 sq ft) | 18x18 tiles | 6x24 plank |
|---|---|---|---|---|---|
| 5 x 8 ft | 40 sq ft | 46 | 5 | 21 | 46 |
| 8 x 10 ft | 80 sq ft | 92 | 10 | 41 | 92 |
| 10 x 10 ft | 100 sq ft | 115 | 12 | 52 | 115 |
| 10 x 12 ft | 120 sq ft | 138 | 14 | 62 | 138 |
| 12 x 12 ft | 144 sq ft | 166 | 17 | 74 | 166 |
| 12 x 15 ft | 180 sq ft | 207 | 21 | 92 | 207 |
| 14 x 16 ft | 224 sq ft | 258 | 26 | 115 | 258 |
| 15 x 20 ft | 300 sq ft | 345 | 35 | 154 | 345 |
| 20 x 20 ft | 400 sq ft | 460 | 46 | 205 | 460 |
Waste runs 10% for a straight grid, 15% for offset or diagonal, and 20% for herringbone. Buy whole boxes from a single dye lot — a later box may not match.
Every constant this calculator uses and where it comes from, so you can check it rather than take our word for it.
Local codes amend the model IRC and adopt different cycles — your building department governs. Manufacturers revise yields; where your product's data sheet disagrees with a default here, use the product's number. See our full methodology.