Tile Calculator: How Many Tiles and Boxes to Buy
Find how many tiles and boxes a floor or wall needs. Enter the area, tile size and grout gap to get the tile count with waste, boxes, covered area and cost.
The joint between tiles.
Allowance for cuts and breakage.
Enter the area to tile and the tile size.
About the tile calculator
The Tile Calculator works out how many tiles you need to cover a surface, and how many to actually buy. Enter the area as a length and a width, or type in a ready-made area. Then enter the tile size, the grout gap and a waste allowance. The calculator returns the net tile count, the number to buy, the number of boxes if you give a box size, the area the purchase will cover in square feet and square metres, and a total cost if you enter a price.
Every length has its own unit, so a room measured in feet can be tiled with tiles sold in millimetres without converting anything first. Tile width and height accept inches, centimetres and millimetres, and the grout gap can be set in any length unit. A gap of zero is allowed for rectified tiles laid tight.
How to calculate how many tiles you need
Steps
- Enter the area to tile as a length and width, each with its own unit, or as a direct area in square feet, square metres or another area unit.
- Enter the tile width and tile height and pick a unit for each. Tiles are usually quoted in inches or millimetres.
- Enter the grout gap. The default is 1/8 inch, about 3 mm. Use 0 if the tiles touch.
- Leave the waste allowance at 10 percent, or change it for your layout.
- Optionally enter the tiles per box and a price, either per box or per tile.
- Read the net tiles, the tiles to buy, the boxes, the covered area and the cost.
Formulas
Tile count
Each tile occupies a grid cell equal to the tile plus one grout joint on each axis:
With tile width , tile height and grout gap , the net count and the purchase count are:
Here is the area and is the waste allowance as a fraction. When you give a box size , boxes are and the tiles you actually buy are boxes times . Counts always round up, because you cannot lay part of a tile you did not buy.
Worked examples
Imperial floor. A 10 ft by 12 ft room is 120 square feet. With 12 in tiles and a 1/8 in gap, each cell is 12.125 in by 12.125 in, which is 147.02 square inches or 1.021 square feet. The room needs 117.54 cells, so 118 tiles net. With 10 percent waste the figure is 129.29, so buy 130 tiles. At 10 tiles per box that is 13 boxes, which covers about 132.7 square feet (12.3 square metres). At 494.
Metric floor. A 3.6 m by 2.4 m floor is 8.64 square metres. With 30 cm by 60 cm tiles and a 3 mm gap, each cell is 30.3 cm by 60.3 cm, or 0.1827 square metres. That gives 48 tiles net and 53 to buy with 10 percent waste, covering 9.68 square metres.
Backsplash. An 8 ft by 2 ft backsplash is 16 square feet. Using 3 in by 6 in tiles with a 1/16 in gap (0.0625 in), each cell is 18.57 square inches. The wall needs 125 tiles net and 137 to buy. In boxes of 50, that is 3 boxes, or 150 tiles.
Why the grout gap matters
The gap is not decoration. On the 10 ft by 12 ft floor above, laying the same 12 in tiles with no gap needs exactly 120 tiles and 132 with waste. A 1/4 in gap needs 116 net and 127 to buy. Ignoring the joint can leave you several tiles over or under, and on small tiles such as mosaics the effect is much larger. If you plan to use a wide joint for a rustic look, enter it.
Waste allowance and spare tiles
A 10 percent allowance covers cuts at the edges, tiles that chip, and a few for matching the pattern. Diagonal, herringbone and other angled layouts waste more offcuts, so use 15 percent or more. Always buy a spare box from the same production lot as the rest. Colour and shade vary between lots, so a tile bought next year may not match, and a leftover box is also your repair kit.
Subtracting openings
The calculator does not take away doors, windows, tubs or built-in cabinets for you. Work out the area to tile yourself, subtract each opening, and type the result into the direct area field. The Area Calculator helps with irregular shapes, and the Area Converter switches the result between square feet and square metres.
Tile sizes in millimetres and inches
A tile sold as 300 x 600 is 300 mm by 600 mm, about 11.8 in by 23.6 in. Nominal inch sizes are often slightly smaller than their name, so check the box. If you need to convert a measurement, use the Length Converter.
Accuracy and limits
The result is a layout estimate for rectangular tiles in a straight grid. It does not model a specific pattern, an uneven surface, trim pieces or cuts around fixtures. Measure the room carefully and confirm the box coverage printed by your supplier before ordering.
Privacy
Nothing is uploaded; every calculation runs in your browser and never leaves your device.
Related tools
For a floor, see the Floor Tile Calculator, and for a backsplash or shower the Wall Tile Calculator. To compare prices, the Unit Price Calculator works out the cost per tile or per square foot. For painting the same room, try the Paint Calculator.
Frequently asked questions
How many tiles do I need for a room?
Divide the area by the area of one tile plus its grout joint, then round up. A 10 ft by 12 ft room with 12 in tiles and a 1/8 in gap needs 118 tiles net. With 10 percent waste you buy 130 tiles, which is 13 boxes of 10.
Why does the grout gap change the tile count?
Each tile takes up its own size plus one joint on each axis. A wider gap means each tile covers slightly more floor, so you need fewer. On the 120 square foot example, a zero gap needs 120 tiles, a 1/8 in gap needs 118 and a 1/4 in gap needs 116.
How much waste should I allow for tile?
Ten percent suits a straight layout in a regular room. Use 15 percent or more for diagonal or herringbone patterns, rooms with many corners, or tiles that cut or chip easily. Waste covers cuts, breakage and pattern matching.
Should I buy extra tiles from the same lot?
Yes. Colour and shade vary between production lots, so tiles ordered later may not match. Keep a spare box from the same lot for future repairs and note the lot number printed on the carton.
How do I subtract a door, window or bathtub?
Calculate the area of the surface, subtract the area of each opening yourself, and enter the result in the direct area field. The calculator then counts tiles for that area only.
Can I mix inches and millimetres?
Yes. The area, tile width, tile height and grout gap each have their own unit, so a room in feet can use 300 mm by 600 mm tiles and a 3 mm gap. Results show covered area in both square feet and square metres.
Is my data sent anywhere?
No. The tile counts, box totals and cost sums run in your browser, so your room measurements and prices are never uploaded or stored on a server. They stay on this device and are not shared with anyone.