Home › Tile calculator
Tile Calculator: How Many Tiles Do I Need?
Enter the area or the room size, your tile size and grout joint, and the calculator tells you how many tiles and boxes to buy, with the right extra for your layout. Then carry the same job over to grout and thinset.
How the tile calculator works
tiles = area × (1 + waste ÷ 100) ÷ ((L + J) × (W + J) ÷ 144), rounded up
boxes = tiles ÷ tiles per box, rounded up
L and W are the tile length and width and J is the grout joint, all in inches; dividing by 144 turns square inches into square feet. Each tile, together with half the joint on every side, takes up an (L + J) by (W + J) patch of floor, so that is what the area is divided by. Waste is added to the area first, and the tile count is then rounded up to a whole tile. Boxes are worked out from the tile count rather than straight from the area, so you never end up one tile short because a box label rounded its square footage.
If you enter a room length and width, they replace the area box. For L-shaped rooms, split the floor into rectangles, add up their areas and type the total into the area box. Leave out cabinets, tubs and islands that will not be tiled, but measure into doorways where the tile runs under the door.
How much extra tile to buy for your layout
Every layout loses tile at the edges, where full tiles are cut to fit, and a few tiles break or turn out to be off-shade. The layout menu sets the usual allowance, and you can type any other figure into the waste box:
- Straight, grid or brick (running bond): 10%. Cuts run square to the walls, so most offcuts are one long strip per row.
- Diagonal: 15%. Every tile along a wall is cut on an angle, and the corners of those cuts are rarely usable elsewhere.
- Herringbone or chevron: 20%. Angled cuts on all four sides of the room and short planks that leave small offcuts.
Lean toward the upper end with large-format tile, where one bad cut wastes a big piece, and in small rooms, where edges are a larger share of the floor. Keep the leftover boxes: tile from a later production run can differ in shade, and Daltile recommends holding back about 10% as attic stock for repairs.
Worked examples
Bathroom floor, 8 x 10 ft, 12 x 24 in porcelain
Room area is 80 sq ft; with 10% for a straight layout that is 88 sq ft. With a 1/8 in joint each tile covers 2.031 sq ft, so the floor needs 43.3 tiles, rounded up to 44 tiles. At 8 tiles a box that is 6 boxes (48 tiles, 4 spare).
Lay the same tile on the diagonal and the 15% allowance raises it to 46 tiles, or 6 boxes.
Herringbone hallway, 150 sq ft, 6 x 24 in planks
With 20% for herringbone the job is 180 sq ft. Each plank with a 1/8 in joint covers 1.026 sq ft, so you need 176 planks, which is 176 sq ft of tile face. With boxes labelled 12 sq ft that is 15 boxes.
Subway tile backsplash or shower wall, 60 sq ft, 3 x 6 in
Small tiles add up fast: with a 1/16 in joint and 10% extra, 60 sq ft of 3 x 6 subway tile is 512 tiles. Many 3 x 6 boxes are sold by the square foot, so enter the area per box from the label to get the box count.
Tiles per 100 square feet, common sizes
| Tile size | Face area per tile | Tiles, no waste | Tiles, +10% |
|---|---|---|---|
| 4 x 4 in | 0.111 sq ft | 847 | 931 |
| 3 x 6 in | 0.125 sq ft | 753 | 828 |
| 6 x 6 in | 0.25 sq ft | 384 | 423 |
| 4 x 12 in | 0.333 sq ft | 288 | 317 |
| 6 x 24 in | 1 sq ft | 98 | 108 |
| 8 x 48 in | 2.667 sq ft | 37 | 41 |
| 12 x 12 in | 1 sq ft | 98 | 108 |
| 12 x 24 in | 2 sq ft | 50 | 55 |
| 18 x 18 in | 2.25 sq ft | 44 | 49 |
| 24 x 24 in | 4 sq ft | 25 | 28 |
| 24 x 48 in | 8 sq ft | 13 | 14 |
Tile sizes are nominal; a "12 x 24" tile is often a little smaller, and a rectified tile is cut to an exact size. If the box gives the actual size, type that in.
Next: grout and thinset for the same job
The calculator's result links straight to the grout calculator with your tile size, joint and area filled in, so you can see how many bags, boxes or pails each grout needs. For the mortar under the tile, use the thinset coverage calculator: large tiles such as 12 x 24 and up usually call for a 1/2 in notch trowel, which roughly halves the coverage of a bag compared with a 1/4 in notch. The thinset coverage chart and grout coverage chart compare every product at once.
FAQ
How do I calculate how many tiles I need?
Measure the area in square feet (length x width for each rectangle, added together), add a waste allowance, and divide by the area one tile covers including its share of the grout joint. For an 8 x 10 ft floor in 12 x 24 in tile with 1/8 in joints and 10% extra, that is 88 sq ft ÷ 2.031 sq ft per tile = 43.3, so 44 tiles.
How much extra tile should I buy?
About 10% for straight, grid and brick layouts, 15% for diagonal layouts and 20% for herringbone or chevron. Daltile also recommends keeping roughly 10% extra as attic stock so a cracked tile can be replaced from the same dye lot later.
Do grout lines reduce the number of tiles?
Slightly. Each joint adds a strip of floor that no tile has to cover. With 12 x 12 in tile and 1/8 in joints, 100 sq ft needs 98 tiles instead of 100. The effect is bigger with small tiles and wide joints, which is why the calculator asks for the joint width.
Should I use tiles per box or square feet per box?
Tiles per box if the label gives it, because you buy whole tiles. Square feet per box on a label is the tile face area times the tile count, so the calculator compares it with the face area of the tiles you need, not with the floor area.
How many tiles are in a square foot?
Divide 144 by the tile's area in square inches: one 12 x 12 tile, two 6 x 12 tiles, four 6 x 6 tiles, eight 3 x 6 subway tiles, nine 4 x 4 tiles. Grout joints make the real number a little lower; the table on this page includes a 1/8 in joint.
Sources
- Layout waste allowances: Tile & Mosaic Depot, How much tile do I need and American Tile Depot, tile waste and layout patterns, read 2026-10-31.
- Attic stock: Daltile, Tile & Natural Stone FAQs, read 2026-10-31.
- Tile and joint geometry: computed; no manufacturer data is needed because a tile covers its own face area.