How to use the tile calculator
- Enter the Area length (ft) and Area width (ft) of the floor, or the length and height of a wall.
- Enter the Tile length (inches) and Tile width (inches). Use the actual size printed on the box, because a tile sold as 12 in can measure slightly less.
- Set the Grout joint width (inches): 0.0625 for 1/16 in, 0.125 for 1/8 in, 0.25 for 1/4 in. Enter 0 to ignore grout lines.
- Enter Tiles per box from the carton.
- Pick a Layout pattern, which fills in Waste (%) at 10, 15 or 20. You can also type your own waste figure.
How the tile count is worked out
Each tile covers its own face plus half of the grout joint on every side, so the calculator measures one tile as (tile length + joint) x (tile width + joint) divided by 144 square feet. Tiles for the area is the area divided by that figure, rounded up. Waste is added on top, and the total is rounded up to whole boxes. The area and tile arithmetic follows the steps in Bob Vila's tile guide, which recommends at least 10 percent extra for a straight layout and up to 20 percent for diagonal or complex patterns, since those leave more tile fragments.
Worked example with the default inputs
A 10 x 8 ft floor is 80 sq ft. A 12 x 12 in tile with a 0.125 in joint takes up 12.125 x 12.125 in, or 1.02 sq ft, so the floor needs 80 divided by 1.02 = 78.4 tiles, which rounds up to 79. Adding 10% waste gives 87 tiles. With 10 tiles per box that is 8.7 boxes, so you order 9 boxes (90 tiles), which leaves 11 tiles beyond the 79 for cuts, breakage and later repairs. With the joint set to 0, the same floor needs 80 tiles, or 88 with waste.
Limits and edge cases
- The tool treats the area as one rectangle. For an L-shaped room or several walls, run each rectangle separately and add the boxes.
- Large-format tiles, small mosaic sheets and rooms with many cuts around tubs, vanities and pipes can need more than 10 percent. Raise Waste if your layout is cut-heavy.
- Some boxes list square feet instead of a tile count. Divide the box coverage by the tile's face area (length x width / 144) to get tiles per box. A 10 sq ft box of 12 x 12 in tile is 10 tiles.
- Need the area first? The rectangle area calculator does it. Comparing floors? See the carpet calculator, or the concrete calculator if the patio needs a new slab first.
Frequently asked questions
How many 12 x 12 tiles do I need for 100 square feet?
With 1/8 inch grout joints you need 98 tiles to cover 100 sq ft, and 108 after 10% waste, which is 11 boxes of 10. With no joint allowance it is 100 tiles, or 110 with waste.
How much extra tile should I buy?
Add 10% for a straight grid layout, about 15% for a diagonal layout, and up to 20% for herringbone, mosaics or rooms with many cuts. The extra also gives you spare tiles for future repairs.
Do grout lines change how many tiles I need?
Yes, slightly. Each tile plus its joint covers a little more floor than the tile face alone, so you need fewer tiles. For 12 in tile with a 1/8 in joint it is about 2 percent, and the effect grows as tiles get smaller.
How do I figure tile for a wall?
Enter the wall length as the area length and the wall height as the area width. For several walls, run each one and add the boxes. Walls with a large window or niche can be split into the rectangles you will actually tile.
Sources: Bob Vila, How Much Tile Do I Need for a Floor or Wall?