Tile is sold by the piece or by the box, and running short mid-project means waiting on a reorder — or worse, discovering your exact tile is now out of stock. Here's how to land on the right count before you buy, by tile size, layout, and room type.
The Basic Formula
Tiles needed = (Room area ÷ Tile area) × (1 + waste factor)
Room area is length × width in square feet. Tile area depends on the tile size — a 12×12" tile covers exactly 1 sq ft, an 18×18" tile covers 2.25 sq ft, and a 6×24" plank tile covers 1 sq ft. Waste factor accounts for cuts, breakage, and future repairs.
Tile Count by Common Sizes (per 100 sq ft, 10% waste)
| Tile Size | Coverage per Tile | Tiles per 100 sq ft |
|---|---|---|
| 6×6" | 0.25 sq ft | 440 tiles |
| 12×12" | 1.0 sq ft | 110 tiles |
| 12×24" | 2.0 sq ft | 55 tiles |
| 18×18" | 2.25 sq ft | 49 tiles |
| 24×24" | 4.0 sq ft | 28 tiles |
| 6×24" plank | 1.0 sq ft | 110 tiles |
Bigger tiles mean fewer pieces to place and fewer grout lines, but each cut wastes more material — a full 24×24" tile trimmed down for an edge throws away far more square footage than a 6×6" tile would.
Quick Reference: Tiles Needed by Room
| Room | Typical Size | 12×12" Tiles | 18×18" Tiles |
|---|---|---|---|
| Small bathroom | 40 sq ft | 44 tiles | 20 tiles |
| Standard bathroom | 60 sq ft | 66 tiles | 30 tiles |
| Kitchen floor | 150 sq ft | 165 tiles | 75 tiles |
| Kitchen backsplash | 30 sq ft | 33 tiles | 15 tiles |
| Living room / open floor | 300 sq ft | 330 tiles | 150 tiles |
Figures above include a standard 10% waste allowance for a straight-lay pattern.
Why Boxes Complicate the Math
Tile isn't sold per piece at most retailers — it's sold by the box, and box coverage varies by tile size and brand (commonly 8–15 sq ft per box). Once you know your total square footage needed, divide by the box coverage and round up. A project needing 165 sq ft with 12 sq ft-per-box tile requires 14 boxes (165 ÷ 12 = 13.75 → round up), not 13. Rounding down to save money is the single most common reason people run short mid-installation.
Layout Pattern Changes the Waste Factor
| Layout | Waste Factor |
|---|---|
| Straight / grid lay | 10% |
| Diagonal (45°) | 15% |
| Herringbone or basketweave | 15–20% |
| Large-format (24"+) on an irregular room | 15–20% |
Common Mistakes When Ordering Tile
- Forgetting grout line width. Grout lines (typically 1/8"–1/4") slightly reduce how much of the wall or floor each tile actually covers on a large job — the calculator above already factors this in, but manual math often doesn't.
- Not buying from the same production lot. Tile color and shade can vary between manufacturing runs (called "dye lot" or "shade variation" on the box). Buying all boxes from the same lot number avoids visible mismatches.
- Skipping the reorder buffer. Buy at least one extra box beyond your waste-adjusted total for future chip or crack repairs — many tile lines are discontinued within a few years.
- Measuring only the floor, not the walls. Bathroom and shower projects often need wall tile calculated separately from floor tile — don't combine square footage across different tile products.
Frequently Asked Questions
How many tiles do I need for a 100 sq ft floor? With 12×12" tiles and 10% waste, plan on about 110 tiles. Larger 18×18" tiles need about 49 tiles for the same area.
How do I convert tile count into boxes? Divide your total square footage (including waste) by the coverage per box listed on the product, then round up to the next whole box.
Should I buy extra tile beyond my calculated amount? Yes — buy at least one extra box for future repairs. Matching tile from the same lot years later is often impossible.
Does tile size affect how much I need to order? Yes. Larger tiles generally waste less material proportionally since fewer cuts are needed, though they cost more per tile and are heavier to handle.