Tile Calculator
Work out how many tiles and boxes to buy for a floor, wall, shower or backsplash. The grout joint is included, waste is added before rounding up, and every price is yours to edit.
How to measure for tile
Measure the surface you want to tile at its longest and widest points, using a tape measure rather than room plans, because walls are rarely perfectly square. For a floor, measure wall to wall at floor level. For a wall or shower, measure the width and the height you plan to tile. Note each measurement to the nearest inch or centimetre.
If the room is L-shaped or has an alcove, divide it into rectangles, measure each one and add the areas. For walls, measure the doors, windows and fitted cabinets that will not be tiled and enter their combined area in the area to subtract field. Small openings such as outlets and pipes can be ignored; the waste allowance covers them.
Finally, read the tile size and the number of tiles per box from the product label or listing. Use the actual size printed in the specifications if it differs from the nominal size. A tile sold as "12 × 24" may measure slightly less, and over a large floor that difference adds up.
The tile formula
Each tile covers its own face plus half of the grout joint on every side, so the area one tile "occupies" is the tile size plus one joint in each direction:
Tile module = (tile length + joint) × (tile width + joint)Tiles needed = (surface area ÷ tile module) × (1 + waste %), rounded upBoxes = tiles needed ÷ tiles per box, rounded upThe calculator rounds up only at the end, after the waste allowance has been added, so you never get a fraction of a tile or box. Units are converted internally, which means you can enter the room in feet and the tile in inches (or the room in metres, the tile in centimetres and the joint in millimetres) without doing any conversion yourself.
Worked example
A kitchen floor measures 12 ft × 10 ft and will be laid with 12 × 12 in tiles, a 1/8 in (0.125 in) grout joint and a 10% waste allowance. The tiles come 10 to a box.
- Floor area: 12 × 10 = 120 sq ft.
- Tile module: (12 + 0.125) × (12 + 0.125) = 147.02 sq in, which is 147.02 ÷ 144 = 1.021 sq ft.
- Tiles to cover the floor: 120 ÷ 1.021 = 117.5 tiles.
- Add 10% waste: 117.5 × 1.10 = 129.3, rounded up to 130 tiles.
- Boxes: 130 ÷ 10 = 13 boxes, which is 130 sq ft of tile.
- At an example price of $2.50 per sq ft, the tile costs 130 × $2.50 = $325.
The same floor in metric (3.6 m × 3 m, 30 × 30 cm tiles, 3 mm joints, 10% waste) also comes out at 130 tiles, or 13 boxes of 10.
A backsplash example: a 20 ft run of counter with tile 1.5 ft high is 30 sq ft. With 3 × 6 in subway tiles, a 1/16 in (0.0625 in) joint and 10% waste, you need 256 tiles. At 40 tiles per box that is 7 boxes. Use a larger waste allowance if the backsplash has many outlets and window returns to cut around.
How much waste to allow
Waste covers cut tiles at the edges, breakages, and pieces rejected for chips or colour variation. As a rule of thumb:
- 10% for a simple rectangular room laid in a straight grid or running bond.
- 15% or more for diagonal layouts, herringbone, chevron, or rooms with many corners, pipes and doorways.
- More for large-format tiles (24 in / 60 cm and up), because one bad cut can cost a whole tile and offcuts are less likely to be reusable.
Natural stone and handmade tiles vary from piece to piece, so plan for some extra to let you blend tiles from several boxes. Whatever you choose, keep at least a few spare tiles after the job. Replacement tiles from a later production batch may not match exactly.
Estimating tile cost
Tile is usually priced per square foot or square metre, but you can only buy whole boxes, so the calculator multiplies your price by the area of the boxes you will actually buy rather than the area of the floor. That gives a more realistic material cost.
The default price is an example only. Tile prices range from inexpensive ceramic to premium porcelain and natural stone, so enter the price from the product you are considering. If you are hiring an installer, add their per-area quote in the installation field. Remember the items this calculator does not include: thinset or adhesive, grout, spacers, backer board or underlayment, waterproofing membrane for wet areas, trim pieces, sealer for natural stone, and tool rental. Ask your supplier for the coverage of the adhesive and grout you choose, because it depends on the trowel notch, the tile size and the joint width.
Tips before you order
- Buy all tiles from the same production lot (shown on the box) where possible.
- Dry-lay a row or two to check your layout before mixing adhesive, and plan cuts so the narrowest strips fall in less visible spots.
- Check how the shop handles returns of unopened boxes; ordering one extra box is often cheaper than a second trip.
Frequently asked questions
How do I calculate how many tiles I need?
Multiply the length by the width of the surface to get its area, then divide by the area of one tile including half the grout joint on each side, which is (tile length + joint) × (tile width + joint). Add a waste allowance, usually 10%, and round up to a whole tile and then to whole boxes.
How much extra tile should I buy?
A 10% allowance is a common starting point for a rectangular room laid in a straight grid. Diagonal, herringbone and other patterns with many angled cuts usually need 15% or more. Keep at least one unopened box after the job for future repairs, because colours can vary from batch to batch.
Does the grout joint change how many tiles I need?
Yes, slightly. Each joint adds a little coverage, so wider joints mean fewer tiles. With small mosaic tiles or wide joints the difference becomes noticeable, which is why this calculator includes the joint in the tile size.
How do I measure a room that is not a rectangle?
Split the floor into rectangles, measure each one and add the areas together. Enter the total as length × width (for example, a length equal to the total area and a width of 1), or run the calculator once per rectangle and add the results.
Should I subtract doors and windows when tiling a wall?
Subtract large openings such as doors, windows and fitted cabinets, but not small items like outlets or pipes. Enter the combined area of the openings in the 'area to subtract' field.