Tile Calculator

What this calculator does

The Tile Calculator estimates how many tiles and boxes a floor, wall, or backsplash project needs. It works from the tile dimensions, the grout gap, and either the room dimensions or a known total area. The result includes the area to cover, the effective coverage of one tile after grout, the tile count without waste, the tile count to buy, and the number of boxes to buy.

Grout lines matter on large projects. A quarter-inch gap around each tile removes a small amount of coverage per tile, but across hundreds of tiles it changes the order quantity. The calculator includes the gap in both directions, applies your waste percentage, and then rounds up to whole boxes.

How to use this calculator

1. Enter the tile length and width in inches.
2. Choose whether to enter the room dimensions or a total area.
3. For room dimensions, enter length and width in feet. For a total area, enter square feet directly.
4. Enter the grout gap in inches. Leave it at zero for a dry-fit or butted tile. A 0.25-inch gap is typical for many ceramic and porcelain tiles.
5. Enter the waste percentage and the number of tiles per box, then click Calculate.

The default example is a 12-by-12-inch tile with a 0.25-inch gap covering a 20-by-15-foot room. It returns 300 square feet, 288 tiles without waste, 317 tiles to buy with 10 percent waste, 24 boxes without waste, and 27 boxes to buy.

Tile formulas

effective tile length = tile length + gap
effective tile width  = tile width + gap
coverage per tile     = effective length × effective width ÷ 144

tiles without waste = ceil(area ÷ coverage per tile)
tiles to buy        = ceil(tiles without waste × (1 + waste % ÷ 100))

boxes without waste = ceil(tiles without waste ÷ tiles per box)
boxes to buy        = ceil(tiles to buy ÷ tiles per box)

All tile and gap inputs are in inches. The division by 144 converts square inches to square feet. The ceiling function rounds up because partial tiles and partial boxes cannot be ordered as fractions.

Assumptions and limitations

• Tile length and width are in inches. Room dimensions are in feet, and total area is in square feet.
• The calculator assumes rectangular tiles laid in a straight grid. Diagonal layouts, herringbone, and mosaic patterns usually need more waste.
• The grout gap is added to both the length and the width. A negative gap can model overlapping tiles, but the effective tile size must remain positive.
• Waste covers cuts, breakage, and future repairs. Ten percent is a common default; complex layouts may need 15 percent or more.
• The box count is only as accurate as the tiles-per-box value you enter. Verify it on the product packaging.
• The estimate does not include thinset, grout, backer board, trim, or spacers.

Frequently asked questions

How many 12-by-12 tiles are in a square foot?

A 12-by-12-inch tile covers exactly one square foot before grout. With a 0.25-inch gap, its effective coverage is about 1.042 square feet, so slightly fewer than one tile is needed per square foot.

How much extra tile should I buy?

Buy 10 percent extra for a simple grid layout and 15 percent or more for diagonal or patterned installations. Keep at least one spare box for future repairs, especially if the tile is a discontinued color.

Why does the calculator round up to whole boxes?

Suppliers sell tile by the box, not by the individual tile. Rounding up ensures the order covers the calculated tile count. Always check the return policy before ordering extra boxes.

Reference table

Example tile quantity

Buy extra tiles for cuts, breakage, and future repairs. Keep at least one spare box when possible.

Source

Reference: Calculator.net — Tile Calculator.

This calculator provides an estimate. Confirm the tile coverage and box quantity with your supplier before purchasing.