How many tiles do I need?

The formula behind the tile count

A tile count is just a division: how much area you need to cover, divided by how much area one tile covers. The only extra steps are adding a waste allowance and rounding up, because you cannot buy part of a tile.

The EveryFix Tile Calculator works in this order. It multiplies length by width to get the area, multiplies that by (1 + waste), works out the face area of one tile as width x height / 144 (so the answer is in square feet), divides, and rounds up. In metric mode it takes meters and centimeters, converts them to feet and inches internally, and does the same math.

Because width and height are entered separately, the same formula handles a 12 x 12 in square, a 6 x 24 in plank, a 3 x 6 in subway tile, or a 60 x 30 cm porcelain tile. Nothing in the formula assumes the tile is square.

• Area of one tile (sq ft) = width (in) x height (in) / 144
• Tiles = area x (1 + waste) / area of one tile, rounded up
• The waste allowance is applied to the whole area, not to each tile

Worked example: a bathroom floor

Take a bathroom floor that measures 8 ft by 6 ft and 12 x 12 in tiles with a 10% waste allowance. The area is 8 x 6 = 48 sq ft. Adding waste gives 48 x 1.10 = 52.8 sq ft. One 12 x 12 in tile covers 144 / 144 = 1 sq ft, so you need 52.8 tiles, which rounds up to 53 tiles.

Now a larger tile. A 14 ft by 12 ft kitchen is 168 sq ft. With 12 x 24 in tiles (288 / 144 = 2 sq ft each) and a 15% allowance for a staggered layout, you need 168 x 1.15 = 193.2 sq ft, divided by 2 = 96.6, rounded up to 97 tiles. If those tiles are sold 8 to a box, 97 / 8 = 12.125, so you would buy 13 boxes, which is 104 tiles and leaves 7 spares. The box size here is only an example; check the one on your product.

The tool's own example works the same way: an 80 sq ft floor with 9 x 9 in tiles and 15% waste is 80 x 1.15 = 92 sq ft, one tile covers 81 / 144 = 0.5625 sq ft, and 92 / 0.5625 = 163.56, rounded up to 164 tiles. In metric, a 3 m by 4 m floor (12 m2) with 30 x 30 cm tiles and 10% waste is 12 x 1.10 / 0.09 = 146.67, rounded up to 147 tiles.

Measuring the area correctly

Most wrong tile counts start with the area, not the tile. For a rectangular room, measure wall to wall at the longest points. For an L-shaped or notched room, split it into rectangles, calculate each one, and add them. A 12 ft by 10 ft main area plus a 6 ft by 4 ft alcove is 120 + 24 = 144 sq ft, and at 10% waste that is 144 x 1.10 = 158.4 sq ft, or 159 tiles of 1 sq ft.

Only count what you will actually tile. Subtract a bathtub or built-in cabinet footprint if tile will not go under it, and decide up front whether tile will run under a removable vanity or toilet. For walls, measure each wall as a rectangle and subtract large windows or doors if the openings are big enough to matter; for a small backsplash, skip the subtraction and let the waste allowance absorb the difference.

If you only have a rough area, the Square Footage Calculator is a quick way to total several rectangles before you run the tile math.

Grout joints and what the calculator ignores

The calculator uses each tile's face dimensions only. In a real installation each tile also owns half of the grout joint on every side, so the area one tile effectively occupies is slightly larger than its face. That means a face-only calculation asks for a few more tiles than a pitch-based count would, which errs on the safe side.

How much more depends on the joint and the tile size. For a 12 x 12 in tile with a 1/8 in joint, the repeat distance is 12.125 in, so each tile occupies 12.125 x 12.125 / 144 = 1.021 sq ft. That is about 2% more than the face area. At 3/16 in the figure is about 3%. On a small tile it grows quickly: a 4 x 4 in tile with a wide 1/4 in joint occupies 4.25 x 4.25 = 18.06 sq in against 16 sq in of face, about 13% more.

A worked case: 30 sq ft of 4 x 4 in tile at 10% waste is 33 sq ft. The face-only count is 33 / (16 / 144) = 297 tiles. Counting the 1/4 in joint instead gives 33 / (18.0625 / 144) = about 263.1, or 264 tiles. The calculator's 297 is therefore about 12% higher. For ordinary 1/8 to 3/16 in joints on larger tiles the gap is small enough to treat as extra cushion; for mosaics and small tiles with wide joints, run the numbers with the tile plus joint size if you want a tighter count, and remember mosaic sheets are usually sold by the sheet.

The calculator does not estimate grout, thin-set, or backer board. Grout depends on joint width, joint depth, and tile size, so use the coverage chart from the grout maker rather than a rule of thumb.

How much waste to add for your layout

Waste is what you lose to cuts at walls, around fixtures, and to the occasional cracked or chipped tile. The calculator defaults to 10%, which suits a straight (grid) layout in a plain rectangular room. Treat the figures below as planning rules of thumb; your installer and the layout of the room decide the real number.

• Straight grid layout, simple rectangle: about 10%
• Offset or brick pattern, many cuts around fixtures: about 10% to 15%
• Diagonal layout, herringbone, or intricate patterns: about 15% to 20%
• Large-format tiles: lean toward the higher end, because each cut or break wastes more area
• First-time installer: add a little more, since mis-cuts are likely

Small rooms, large tiles, and where percentages break down

A percentage is a good model for big rooms and a poor one for small rooms. A 5 ft by 4 ft powder room is 20 sq ft, and 10% waste is 22 tiles of 1 sq ft, only two spares. But a room that small has cuts along every edge, and one bad cut can use a whole tile, so two spares may not be enough. Add more than the default for tiny rooms and for rooms where the walls are not square.

Large-format tiles behave differently again. With a 12 x 24 in tile at 15% waste in a 168 sq ft kitchen, 15% is about 25 sq ft, or roughly 13 tiles. At 10% the order is 93 tiles instead of 97 (168 x 1.10 / 2 = 92.4). That gap of four tiles is cheap insurance compared with finding out you are one tile short on a discontinued product.

Also check the pattern before you order. Directional or veined tiles that must be laid in a set sequence, and any tile that needs a particular cut order, can use more material than the formula implies. If the design is complicated, ask your supplier or installer for a layout-specific count and use this formula as a cross-check.

Spare tiles, boxes, and dye lots

Tile is sold by the box, so after the formula, convert to boxes and round up. Then think about the tiles you will not install. Keep a few spares for future repairs: a cracked tile in five years is much easier to replace if you still have the original.

The usual advice is to buy all your tiles for a room from the same production batch. Shade and sometimes size can differ between production runs, which is why retailers print a lot or batch number on the box. Buy everything in one purchase and check that the numbers on the boxes match before you leave the store or accept a delivery.

Open the boxes before you start and mix tiles from several boxes as you lay them. This spreads any slight shade variation across the floor instead of leaving one visible patch.

Common mistakes

These errors turn up again and again when people calculate tile.

• Mixing units: the formula expects the room in feet and the tile in inches, so entering a centimeter tile size against a feet-based area (or the reverse) throws the count off dramatically.
• Forgetting to convert square inches to square feet by dividing by 144.
• Rounding down instead of up, which leaves you short by a partial tile.
• Skipping waste on a small, cut-heavy room because the percentage looks like a tiny number.
• Ordering exactly what the formula returns and nothing for spares or repairs.
• Buying across two batches or two shipments without checking the lot number.