A tile calculator estimates how many tiles you need to cover a floor, wall, or backsplash, including a standard 10% waste allowance for cuts, breaks, and future repairs. Enter the room's area in square feet, the tile dimensions in inches, and (optionally) the cost per tile, the calculator returns the total tile count and project cost.
The formula converts square feet to square inches (×144), divides by the per-tile area, and adds 10% on top before rounding up. The 10% buffer is the trade contractor standard; complex layouts (diagonal patterns, lots of pillars or fixtures, or large-format tile) often warrant 15-20%.
Key takeaway
Always over-buy tile. The waste allowance isn't optional padding, it covers cuts at edges, breakage during installation, and the dye-lot problem: if you run out mid-job, the next box you buy may not match because tile color varies subtly between manufacturing batches. A 10% buffer plus a few spare tiles set aside for future repairs is the safe minimum.
How it's calculated
The math:
tile area (sq in) = tile_length × tile_width total area (sq in) = floor area in sq ft × 144 tile count = ⌈ total area ÷ tile area × 1.10 ⌉
The × 144 converts square feet to square inches (since 1 ft = 12 in, and 12² = 144). The × 1.10 adds the 10% waste factor. The ceiling function rounds up, you can't buy a fractional tile.
For complex jobs you may want a higher waste factor:
- Standard rectangular room, square tiles: 10%
- Diagonal patterns, herringbone: 15%
- Large-format tile (24"×24" and up): 15%
- Lots of cuts (curves, fixtures, pipes): 15-20%
- Mosaic tile, complex patterns: 20%
This calculator uses the standard 10%; for complex jobs, multiply the "exact tiles" output by your preferred factor manually.
Source: Standard area-coverage method, area ÷ per-tile area, with 10% overage
Examples
100 sq ft floor with 12×12 tiles
- Area to tile 100 sq ft
- Tile length 12 in
- Tile width 12 in
- Cost per tile (optional) $2.5
A 100 sq ft floor with 12×12 (1 sq ft) tiles needs exactly 100 tiles for the area, but 110 with the 10% waste allowance. At $2.50 per tile, that's $275 in materials. This is the simplest case, square tiles whose area exactly matches the unit conversion.
60 sq ft backsplash with 4×4 subway tile
- Area to tile 60 sq ft
- Tile length 4 in
- Tile width 4 in
- Cost per tile (optional) $0.95
A 60 sq ft backsplash with small 4×4 tile needs 594 tiles (540 exact
- 10% waste). At $0.95 each, that's about $564 in tile. Small-format backsplash tile generates more cuts and breakage in practice, consider bumping the waste allowance to 12-15% if you're new to tiling.
Frequently asked questions
How much extra tile should I buy?
The standard contractor allowance is 10% for simple square or rectangular layouts. Bump that to 15% for diagonal patterns, large-format tile (24" and up), or rooms with lots of cuts around fixtures. For mosaic or complex patterns, 20% is safer. Always round up, you can't buy a fractional tile, and running out mid-job means risking a dye-lot mismatch.
What is a dye lot and why does it matter?
Tile is fired in batches, and color and finish vary subtly between batches, the dye lot (or batch number) is the manufacturer's identifier for one production run. If you run out of tile and the store only has a different dye lot in stock, you'll see a visible color difference between the new and old tile. This is why the 10% waste rule exists: it's not just for breakage, it's insurance against the dye-lot problem.
Should I include grout lines in my calculation?
Generally no, manufacturers list tile dimensions assuming standard 1/8" grout joints, and the 10% waste allowance absorbs the small difference. For wider grout lines (1/4" and up), or if you're using very small tile where grout makes up a meaningful percentage of the surface, you can reduce the tile count slightly, but the savings rarely outweigh the risk of running short.
How do I calculate tile for a non-rectangular room?
Break the room into rectangles, calculate each separately, and sum. For rooms with curves or odd angles, calculate the smallest enclosing rectangle and use that area, the cuts to fit the actual shape become part of your waste, which is what the 10% allowance is for. Tile that gets cut off can't usually be reused, so this isn't double-counting.