Tile Calculator
Enter the floor or wall area, the tile size and the grout gap to get the number of tiles and boxes to buy — with a waste allowance for cuts and breakage.
For a wall, use the wall width as the area length and the wall height as the area width. Coverage per tile includes one grout joint: (tile + gap) × (tile + gap).
How the math works
across = ceiling(area length ÷ module width) · down = ceiling(area width ÷ module height)
tiles = across × down × (1 + waste %)
boxes = ceiling(tiles ÷ tiles per box)
Each tile takes up its own face plus one grout joint, so the repeating unit — the module — is tile size + gap. A 12 in tile with a 1/8 in joint therefore repeats every 12.125 in, which is why 100 sq ft needs about 98 tiles rather than 100. The joint is small, but leaving it out of the layout is how people end up one column short.
The calculator rounds up per row and per column, not on total area, because the last tile in a row is nearly always cut from a full tile: a strip 4 in wide still consumes a 12 in tile. Multiplying those two whole numbers gives the minimum number of tiles that will physically cover the area with a grid layout.
Waste is applied last, and it is not padding: it is the material that goes into edge cuts, corners, outlets and the tile that chips on the way in. Ten percent is normal for a straight lay, fifteen for a diagonal layout, and around twenty for herringbone or a room with many corners.
Grout gap: how wide?
Rectified porcelain is cut square after firing, so it can take a tight joint — 1/8 in (3 mm), occasionally 1/16 in (1.5 mm). Standard ceramic has slightly rounded edges and looks best with 3/16 to 1/4 in (5–6 mm); a tight joint on a cushion-edged tile shows the bevel and makes lippage obvious. Large-format tiles usually sit at 1/8 in, but they need a very flat substrate — a 1/16 in lip across a 24 in tile is visible and catches a mop.
The gap changes the tile count only slightly — about 2% for a 1/8 in joint on 12 in tile — but it changes the layout and the grout quantity. Follow the manufacturer's recommendation and use spacers rather than judging by eye.
Coverage per tile
| Tile size | Coverage with 1/8 in joint | Tiles per 100 sq ft* |
|---|---|---|
| 6 × 6 in | 0.26 sq ft | 384 |
| 12 × 12 in | 1.02 sq ft | 98 |
| 12 × 24 in | 2.03 sq ft | 50 |
| 18 × 18 in | 2.28 sq ft | 44 |
| 24 × 24 in | 4.03 sq ft | 25 |
*Rounded up, before waste. If the box lists square feet instead of a tile count, tiles per box = box coverage ÷ tile face area (12 × 12 in = 1 sq ft, 12 × 24 in = 2 sq ft).
Floors, walls and openings
The math is the same for a floor and a wall; only the measurements change. For a floor, length × width of the room. For a wall, width × height, and measure each wall separately if they differ — then add the areas together before entering them here.
Deduct openings larger than a couple of square feet — a door is about 21 sq ft, a window about 12 sq ft. Leave small niches and outlets in the count, and add the inside faces back if you are tiling a reveal. Bathroom walls usually need 5% extra on top of the normal waste because of the fixtures and short runs.
Buying tiles
Buy the whole job at once: boxes carry a shade and caliber code, and a later batch can differ enough in tone or size to show in the finished floor. Keep one spare box — matching a discontinued tile later is usually impossible, and a repair with no spare means re-tiling the whole area.
FAQ
- How many tiles do I need for 100 square feet?
- With 12 × 12 in tiles and a 1/8 in grout gap, about 98 tiles: each tile covers 1.02 sq ft once its joint is included, and 100 ÷ 1.02 = 98. Add 10% for cuts and you need 108 tiles, or 11 boxes of 10.
- How many tiles are in a box?
- It depends on the tile size. Boxes usually print both the tile count and the square footage they cover; 12 × 12 in boxes commonly hold 10 to 15 tiles, while 12 × 24 in boxes hold about 6 to 8. If only square feet are listed, divide the box coverage by the tile face area.
- What grout gap should I use?
- About 1/8 in (3 mm) for rectified porcelain, and 3/16 to 1/4 in (5–6 mm) for ceramic tiles with slightly rounded edges. Large-format tiles typically use 1/8 in and natural stone usually 1/8 to 3/16 in. Follow the tile manufacturer’s recommendation for the specific product.
- Should I subtract doors and windows from wall tile?
- Deduct openings larger than about 2 sq ft, such as a door (roughly 21 sq ft) or a window (roughly 12 sq ft). Leave small niches and outlets in the count, and add the inside faces back if you are tiling a reveal or a niche.
- How much waste should I add?
- 10% for a straight lay in a simple rectangular room, 15% for a diagonal layout, and 20% for herringbone or a room with many corners, doorways and cuts. Keep one spare box after the job, because dye lots and calibers change between batches.