How this instrument works
Once you know one tile's footprint, tiling math is straightforward division: total area to cover, divided by the area of a single tile, gives the raw tile count, rounded up since partial tiles still require a whole tile to cut from. The one wrinkle worth tracking carefully is unit consistency — tile dimensions are commonly given in inches while room area is measured in square feet, so this calculator converts a tile's length and width in inches into square feet automatically before dividing.
Waste allowance is where layout pattern matters more than most people expect. A straight-lay pattern, with tile edges running parallel to the walls, produces mostly full tiles and small, predictable cuts along the perimeter — a 10% allowance is commonly cited as adequate for that kind of layout. A diagonal or herringbone pattern creates many more angled cuts, especially along the border, and commonly needs 15-20% or more to cover the extra waste those cuts generate. Treat the waste figure as something to set based on your actual layout, not a single number that fits every job.
This calculator reports tiles needed as whole tiles, not boxes — if your tile is sold in boxes covering a fixed area, divide the tiles-needed figure (or the area-with-waste figure) by your box's tile count or coverage to get the number of boxes to order, since box sizes vary by product and this calculator doesn't assume one.
- Enter the area to be tiled, in square feet.
- Enter the tile's length and width, in inches.
- Set a waste allowance — 10% is typical for a straight-lay pattern; use 15-20% for diagonal or intricate layouts.
- Read Area per tile and Tiles needed, already rounded up to a whole tile.
Worked example — a 150 sq ft floor in 12×12 in tile
A 150 sq ft room is being tiled in standard 12×12 inch tile laid straight, using a 10% waste allowance. One tile's area = (12 × 12) / 144 = 1 sq ft exactly. Tiles needed = ceil(150 × 1.10 / 1) = ceil(165) = 165 tiles.
Switch to an 18×18 inch tile on the same floor laid diagonally, where a 15% allowance is more appropriate: tile area = (18 × 18) / 144 = 2.25 sq ft; for a 200 sq ft room, tiles needed = ceil(200 × 1.15 / 2.25) = ceil(102.222) = 103 tiles — noticeably fewer individual tiles despite the larger room, since each larger-format tile covers more than twice the area of the 12×12 tile.
Questions
How many tiles do I need for a room?
Divide the room's area by one tile's area (in the same units), add a waste allowance for cuts, and round up to a whole tile. This calculator converts a tile's length and width from inches into square feet automatically, so you can enter your room area in square feet and the tile size in inches without converting anything by hand.
How much extra tile should I buy for waste?
10% is a commonly cited figure for a straight-lay pattern with edges running parallel to the walls, where cuts are mostly limited to the perimeter. Diagonal or herringbone layouts create far more angled cuts and commonly call for 15-20% or more. Complex rooms with lots of jogs, niches, or fixtures to tile around may need even more margin on top of the pattern-driven figure.
Does this calculator subtract doorways or fixtures from the area?
No — area is a direct input here, so it reflects whatever figure you enter. Measure or calculate the actual area to be tiled (subtracting any permanently uncovered space like a fixed cabinet footprint, if applicable) before entering it, since the calculator has no way to know about openings or obstructions you haven't already accounted for.
Why does a larger tile need fewer total pieces for the same area?
Because each individual tile covers more square footage, so it takes fewer of them to add up to the same total area — a straightforward consequence of the area-per-tile figure in the denominator. This doesn't necessarily mean a larger tile is more economical overall, since large-format tile is often priced higher per square foot and can require a bigger, costlier trowel notch and mortar bed for installation.
How do I convert tiles needed into boxes to order?
Check your specific tile's box coverage (in square feet) or tile count per box, printed on the box or product page, then divide either the tiles-needed figure or the area-with-waste figure by that box quantity, rounding up. Box sizes vary by manufacturer and tile size, so this calculator reports individual tiles rather than assuming a fixed box coverage.