The tile calculator math is simple: divide the area you are tiling by the square footage of one tile, then add 10 percent for straight layouts or 15 percent or more for diagonal and patterned layouts. Round up to full boxes. For example, an 8 x 10 ft floor with 12 x 12 in tile needs 88 tiles, or 9 boxes of 10.
The calculator works for floors, backsplashes, and shower walls. For a wall, use its width and height as the length and width.
How to measure for tile
- Measure the length and width of the area. For a floor, go wall to wall. For a wall or backsplash, measure the width and the height you plan to tile.
- Break odd shapes into rectangles. Measure each section, work out its area, and add them together. Our square footage calculator adds up to three areas for you. Then enter the total as a length with a width of 1.
- Subtract what will not be tiled. Leave out cabinet footprints on a floor, and windows, niches, or the space behind a range on a wall, if they are large.
- Measure a tile. Use the listed size in inches, such as 12 x 24. The calculator converts it to square feet.
- Check the box. Note how many tiles come in each box. The calculator rounds up to whole boxes.
- Choose the extra. Use the table below to pick a percentage for your layout and room shape.
The formula (with a worked example)
- Tile coverage = tile length (in) x tile width (in) / 144
- Tiles = area (sq ft) / tile coverage x (1 + extra % / 100), rounded up
- Boxes = tiles / tiles per box, rounded up
The calculator's defaults are an 8 x 10 ft area, 12 x 12 in tile, 10 tiles per box, and 10 percent extra:
- Area: 10 x 8 = 80 sq ft
- Tile coverage: 12 x 12 / 144 = 1.00 sq ft
- Tiles: 80 / 1.00 x 1.10 = 88
- Boxes: 88 / 10 = 8.8, rounded up to 9
The calculator shows "You need 88 tiles (9 boxes)." and "Area: 80 sq ft. Each tile covers 1.00 sq ft. Includes 10% extra." Nine boxes hold 90 tiles, two more than the calculated count, which gives you a couple of spares for later repairs.
Tiles needed by tile size
This chart shows how tile size changes the count. The last two columns use the calculator's formula for the default 8 x 10 ft floor.
| Tile size | Sq ft per tile | Tiles per 100 sq ft (no extra) | 8 x 10 ft floor, 10% extra | 8 x 10 ft floor, 15% extra |
|---|---|---|---|---|
| 3 x 6 in | 0.125 | 800 | 704 | 736 |
| 6 x 6 in | 0.25 | 400 | 352 | 368 |
| 12 x 12 in | 1.00 | 100 | 88 | 92 |
| 6 x 24 in | 1.00 | 100 | 88 | 92 |
| 12 x 24 in | 2.00 | 50 | 44 | 46 |
| 18 x 18 in | 2.25 | 44.4 | 40 | 41 |
| 24 x 24 in | 4.00 | 25 | 22 | 23 |
| 8 x 48 in | 2.67 | 37.5 | 33 | 35 |
A 12 x 12 and a 6 x 24 tile cover the same area, so they need the same count. The plank shape can still waste more in practice, because long tiles can leave long offcuts at the walls.
How much extra tile to buy by layout
| Layout or room | Extra to add | Why |
|---|---|---|
| Straight (grid) layout, simple room | 10% | Cuts at the edges and some breakage |
| Diagonal layout or intricate pattern | 15% | Angled cuts at every wall |
| L-shaped rooms, curved walls | 15 to 20% | More cuts to fit angles and curves |
| Diagonal pattern, upper range | Up to 25% | Angled cuts and small pieces break more easily |
These ranges come from Clé Tile's ordering guidance. The calculator note uses the same starting points: 10 percent for straight layouts and 15 percent for diagonal or herringbone. When in doubt between two numbers, pick the higher one. Running short means waiting on a reorder, and a later box may not match your original run.
Large tile: offsets and grout joints
Big tiles look simple, but industry standards add a few rules that affect the layout, and the layout affects waste.
Keep offsets at 33 percent or less
The Ceramic Tile Foundation explains that under ANSI A108.02, when any side of the tile is longer than 15 in, a running bond offset should be no more than 33 percent unless the tile manufacturer says otherwise. Large tiles can have some edge warpage, and a 50 percent offset puts the center of one tile beside the ends of its neighbors, where any height difference (lippage) shows most. A one-third offset changes where your cut pieces fall, so plan your rows before you buy.
Grout joints
The Tile Council of North America notes that ANSI A108.02 requires grout joints at least three times the actual size variation of the tiles supplied, and advises avoiding patterns that put the center of one large tile near the end of another when you use a narrow grout joint. For running bond with any tile side over 15 in, the Ceramic Tile Foundation cites ANSI minimums of 1/8 in for rectified tile and 3/16 in for calibrated tile, widened by the amount of edge warpage.
Mortar: how many bags of thinset
Tile count is only half the shopping list. Thinset coverage depends heavily on the trowel notch, and the deeper the notch, the fewer square feet a bag covers. As an example, Custom Building Products lists these coverage figures for a 50 lb bag of its VersaBond Professional mortar:
| Trowel notch | Coverage per 50 lb bag |
|---|---|
| 1/4 x 1/4 x 1/4 in square notch | 90 to 100 sq ft |
| 1/4 x 3/8 x 1/4 in square notch | 60 to 67 sq ft |
| 1/2 x 1/2 x 1/2 in square notch | 42 to 47 sq ft |
For the default 80 sq ft floor, that is one bag with the smallest notch but two bags with the 1/2 in notch. Use the trowel size your tile and mortar instructions call for, and check the coverage on the bag you actually buy, since products differ.
Tips and common mistakes
- Buying everything at once. Clé Tile recommends buying all your tile, including the extra, together so it comes from the same production run. Tile bought later can differ in color.
- Forgetting trim pieces. Bullnose, pencil liners, and edge trims are sold separately. Count them by the linear foot of exposed edge and check the length of each piece.
- Using the wrong extra for the layout. A herringbone or diagonal floor at 10 percent is an easy way to run short.
- Ignoring the box count. Tile is sold by the box, so the calculator rounds up. Look at how many spare tiles that leaves; if it is only one or two on a diagonal job, consider one more box.
- Not planning the edges. Dry-lay a row or sketch the layout so you do not end with thin slivers at a wall or doorway. Centering the layout can use more cuts, so settle it before you order.
- Throwing out the spares. Keep a few tiles and write the room on the box. Discontinued tile is almost impossible to match later.
Frequently asked questions
How many 12 x 12 tiles do I need for a 10 x 10 room?
A 10 x 10 room is 100 sq ft, and each 12 x 12 tile covers 1 sq ft, so you need 100 tiles before extra. With 10 percent for cuts and breakage, plan on about 110 tiles; with 15 percent for a diagonal layout, about 115.
How many 12 x 24 tiles are in 100 sq ft?
A 12 x 24 tile covers 2 sq ft, so 100 sq ft takes 50 tiles before extra, or about 55 with 10 percent added. Check the box label to see how many tiles or square feet each box holds.
How much extra tile should I buy?
Clé Tile recommends 10 percent for straight layouts and 15 percent for intricate patterns or diagonal layouts, with 15 to 20 percent for L-shaped rooms or curved walls and up to 25 percent for some diagonal installations. More cuts mean more waste.
Does the grout joint change how many tiles I need?
Slightly, and in your favor. Grout lines add a little to the space each tile takes up, so you need a few fewer tiles than the plain area math says. The calculator ignores grout, which leaves you a small extra cushion.
Should I keep leftover tile?
Yes. Clé Tile points out that styles and colors get discontinued, making an exact match impossible later. A few spare tiles from the original run make a cracked-tile repair simple.
What grout joint width should I use with large tile?
Under ANSI A108.02, the grout joint must be at least three times the actual size variation of the tiles. For running bond layouts with a tile side longer than 15 in, the Ceramic Tile Foundation cites minimums of 1/8 in for rectified tile and 3/16 in for calibrated tile. Follow the tile manufacturer's recommendation.