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Estimate tile count with room for cuts and breakage.
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Tile calculator guide
Tile count combines the floor area, the size of each tile, and a cutting allowance for the pieces lost to edges, corners, and breakage. This calculator multiplies the room length and width to find the floor area, converts the tile dimensions from inches into the coverage of one tile in square feet, divides area by coverage, applies your allowance, and rounds up to whole tiles. It exposes the waste step because a mathematically exact area rarely matches the whole boxes and cuts required on site: every wall you meet produces offcuts, and a diagonal or herringbone pattern produces many more. Use the tile count to work out boxes from the pieces-per-box figure on the carton, and keep a few spares for repairs, because tile lines and shade batches are discontinued frequently.
Floor area (sq ft) = room length (ft) × room width (ft). Tile coverage (sq ft) = tile length (in) × tile width (in) ÷ 144. Tile count = floor area ÷ tile coverage × (1 + cutting allowance ÷ 100), rounded up.
Worked example with the defaults: a 12 ft × 10 ft room has 12 × 10 = 120 sq ft of floor area. A 12 in × 12 in tile covers 12 × 12 ÷ 144 = 1 sq ft, so the room needs 120 ÷ 1 = 120 tiles before cuts. Applying the default 10% cutting allowance gives 120 × 1.10 = 132, and because that is already a whole number the calculator displays 132 tiles. Switching to 18 in × 18 in tiles changes the coverage to 18 × 18 ÷ 144 = 2.25 sq ft, so 120 ÷ 2.25 × 1.10 = 58.7, rounded up to 59 tiles; at 12 tiles per box you would buy 5 boxes.
Enter the room dimensions in feet and the tile dimensions in inches; the calculator divides the tile area by 144 to convert square inches to square feet. For metric tiles, convert millimetres to inches first (300 mm = 11.81 in), or measure the room in metres and the tile in centimetres and use the same formula with 10,000 cm² per m². Grout joints add a small amount of coverage per tile that the calculator ignores, which errs on the side of a few extra tiles.
The result is a purchase estimate in whole tiles. Diagonal layouts, pattern matching, corners, fragile natural stone, and future repairs may justify a higher allowance and more spare stock.
Do not divide room area by a tile dimension without finding the tile’s area; 120 sq ft divided by 12 inches is meaningless, while 120 divided by the 1 sq ft coverage of a 12 × 12 tile is 120 tiles. Do not ignore box rounding, because tile is sold in full cartons and the count per box varies from 5 to 20. Do not assume every layout uses the same 10% allowance: a straight grid in a rectangular room may manage with 10%, a diagonal or herringbone pattern often needs 15–20%, and large-format or handmade tiles break more often in cutting. Subtract fixed islands or cabinets only where the tile genuinely stops.
Confirm layout, lot consistency, substrate preparation, and manufacturer installation requirements before ordering.
Sources
How it works
Estimate tile count with room for cuts and breakage. This tool explains the calculation so you can adjust the assumptions to match your situation.
Worked example
With Room length = 12 ft · Room width = 10 ft · Tile length = 12 in · Tile width = 12 in · Cutting allowance = 10 % → 132 tiles (tiles including cutting allowance). Change an input above and this example updates with your numbers.
Common questions
Use about 10% for a simple grid layout in a rectangular room and 15–20% for diagonal, herringbone, patterned, irregular, or fragile installations. For the default 120 sq ft room with 12 × 12 tiles, 10% means 12 extra tiles and 20% means 24.
Yes. A labeled spare box, or at least 5–10 pieces, makes future repairs possible if the product or color lot is discontinued, and tile lines change often. Store spares flat and dry with the batch number written on the carton.
Each 12 × 12 in tile covers exactly 1 sq ft, so 120 sq ft needs 120 tiles before cuts. With the default 10% cutting allowance the calculator returns 132 tiles; at 10 tiles per box that is 14 boxes with 8 spares left over.
Divide the tile count by the pieces per box printed on the carton and round up. Boxes are often labeled by coverage instead, so you can also divide the planning area (132 sq ft in the default case) by the square feet per box and round up the same way.