Tile Calculator

How it works

Each tile, together with half of the grout joint on every side, occupies a rectangle one joint wider and one joint longer than the tile itself. Dividing the area to be tiled by that rectangle gives the number of tiles that cover it. Ignoring the joint overstates the count slightly; for 12 in tiles with 1/8 in joints the difference is about 2%.

Tiles are cut at every wall and around every obstacle, and some break. The waste allowance covers those cuts. Layouts that cut more tiles need more: a diagonal lay cuts a triangle at every wall and a herringbone cuts at every edge. Each pattern has its own editable allowance, starting at a typical value.

The tile count with waste is rounded up to whole tiles, and then to whole boxes.

Formula

tile module   = (tile length + joint) × (tile width + joint)
tiles to cover = area ÷ tile module   (same units)
tiles to buy  = tiles to cover × (1 + waste % ÷ 100), rounded up (at least 1)
boxes         = tiles to buy ÷ tiles per box, rounded up

Example

A 120 sq ft floor in 12 in × 12 in tile with 1/8 in joints: each tile occupies 12.125 in × 12.125 in = 147.02 sq in, so 120 × 144 ÷ 147.02 = 117.5 tiles cover the floor.

With 10% waste for a straight lay that is 129.3, so 130 tiles; at 10 tiles per box, 13 boxes.

Assumptions and limitations

• The waste allowances (straight 10%, offset 10%, diagonal 15%, herringbone 20%) are typical values, not figures from a standard. Small rooms, many corners, large tiles and natural stone with rejects need more.
• Tile sizes are taken as entered. Many tiles are sold by a nominal size that differs slightly from the actual size printed on the carton; the count is only as accurate as the size entered.
• The area is the net area to be tiled, without cabinets, tubs and other areas that will not be tiled.
• Herringbone and other patterns that use rectangular tiles are counted on the same tile-plus-joint area as a grid; the pattern changes the cuts, which the waste allowance covers.
• The result is an estimate. It is not a substitute for the tile manufacturer's instructions or a layout by the installer.

Frequently asked questions