Tile Calculator

Tiles and boxes for a floor or wall, with the grout joint and a waste allowance built in.

Units

Feet and inches Metric

Length

Width

Add or subtract a second area

Tile size

Tile length

Tile width

Grout joint

Layout

Box label lists

Tiles per box Area per box

Tiles per box Printed on the box or the product page.

Tile to buy

Boxes –

Tiles needed–
Exact tiles, no waste–
Area–
Tiles per box–
Tiles bought–
Leftover tiles–

How to use the tile calculator

Enter the length and width of the floor or wall. For an L-shaped room, add a second rectangle. To leave out a tub or island, subtract one.
Pick a tile size or enter your own, and the grout joint.
Pick the layout. It sets the waste allowance, or choose a custom percentage.
Enter the tiles per box, or the area per box, from the box label.

Tile formulas

Area            = length × width (± second area)
Tiles per sq ft = 144 ÷ ((tile length + joint) × (tile width + joint))
Exact tiles     = area × tiles per sq ft
Tiles needed    = exact tiles × (1 + waste %), rounded up
Boxes           = tiles needed ÷ tiles per box, rounded up
Leftover        = boxes × tiles per box − tiles needed

Tile sizes and the joint are in inches. Each tile covers its own face plus one joint on two sides, which is why the joint is added to both dimensions. When the box lists coverage instead of a count, tiles per box = area per box ÷ the face area of one tile, rounded to a whole tile.

Worked example

A 10 x 12 ft kitchen floor in 12 x 24 in porcelain with a 1/8 in joint, laid straight, in boxes of 8 tiles.

Area: 10 × 12 = 120 sq ft (11.15 m²).
Tiles per sq ft: 144 ÷ ((12 + 0.125) × (24 + 0.125)) = 0.49228.
Exact tiles: 120 × 0.49228 = 59.07 tiles.
With 10% waste: 59.07 × 1.10 = 64.98, so 65 tiles.
Boxes: 65 ÷ 8 = 8.1, so 9 boxes, or 72 tiles.
Leftover: 9 × 8 − 65 = 7 tiles beyond the waste allowance.

How much waste to allow

A common rule of thumb is 10% extra for a straight lay and 15% for a diagonal or herringbone layout, which cut more tiles at the edges. Allow more for small rooms with many corners, for large tiles where one bad cut wastes more area, and for natural stone with color variation you may want to sort. These are field rules, not a published standard.

Tips

Buy every box from the same production lot and check the lot number on each box. Shade and size can change between lots.
Keep a few leftover tiles for future repairs. A discontinued tile is hard to match.
Dry-lay a row in each direction before you mix thinset to check the cuts at the walls and doorways.
This calculator does not estimate grout or thinset. Use the coverage chart from the maker of the product you buy, since it depends on the tile thickness, joint and trowel size.

Tile calculator FAQ

How many tiles do I need for a 10x12 floor?

With 12 x 24 in tiles, a 1/8 in joint and 10% waste, a 120 sq ft floor needs 65 tiles. In boxes of 8, that is 9 boxes with 7 tiles left over.

How do I calculate tiles per square foot?

Divide 144 by the tile length plus the joint times the tile width plus the joint, all in inches. A 12 x 12 in tile with a 1/8 in joint gives 144 ÷ (12.125 × 12.125) = 0.98 tiles per sq ft.

How much extra tile should I buy?

A common rule of thumb is 10% for a straight lay and 15% for diagonal or herringbone patterns. Add more for small rooms with many cuts or for large format tile.

How many boxes of tile do I need?

Divide the tiles needed, including waste, by the tiles per box and round up. If the box lists square feet instead, divide that by the face area of one tile to get the tiles per box.

Does the grout joint change how many tiles I need?

Slightly. On a 120 sq ft floor of 12 x 24 in tile, going from a 1/16 in to a 1/4 in joint drops the exact count from 59.5 to 58.2 tiles. The joint matters more with small tiles such as 3 x 6 in subway.

Can I use metric tile sizes?

Yes. Switch to metric to enter the room in metres, the tile in millimetres and the box coverage in square metres. The grout joint options show both inches and millimetres.