CALCULATION METHOD
How much tile do I need?
Multiply each rectangular section’s length by width, add the areas, subtract openings or excluded spaces, and apply a cutting allowance. Divide the order area by one tile’s face area and round up. Then divide by tiles per box and round up again.
Net area = total rectangular area − excluded area
Order area = net area × (1 + waste allowance)
Tiles = order area ÷ tile face area, rounded up
Boxes = tiles ÷ tiles per box, rounded up
12 × 15 ft tile example
A 12 × 15 ft floor has 180 sq ft. With 10% extra, the order area is 198 sq ft. A 12 × 24 in tile covers 2 sq ft, so the estimate is 99 tiles. At eight tiles per box, buy 13 boxes, which provide 208 sq ft.
Floor and wall tile calculator
The same area method works for floors, shower walls, feature walls, and backsplashes. For walls, subtract large windows or openings only when they will not be tiled. Small cutouts may not reduce purchasing needs because they still create offcuts.
12 × 24 tile calculator and box calculator
Enter the actual tile dimensions and tiles per box. This calculates theoretical face coverage; if the carton prints a different square-foot coverage, use the carton label as the final ordering reference.
How much extra tile should I buy?
The calculator starts at 10%. Straight layouts in simple rooms may use less, while diagonal patterns, large-format tile, complex cuts, breakage, or future repairs can require more. Confirm the allowance with the installer and product guidance.
Grout and thinset calculator
Grout and mortar usage cannot be derived reliably from area alone. Grout varies with tile dimensions, thickness, joint width, and installation loss. Mortar varies with tile, substrate, trowel, coverage requirements, and application method. Enter the coverage from the exact bag or technical data sheet.
The Home Depot tile layout guide for rectangular area, L-shaped sections, tile face area, and a typical 10% allowance; Lowe’s tile flooring calculator for a 10% trim and waste suggestion; MAPEI product calculators for product-specific grout and mortar coverage caveats. Accessed September 11, 2026.