Floor tile calculator

Enter the room and the tile, and get the number of tiles and boxes to buy. The grout joint is counted, and every layout pattern is compared at its usual waste allowance.

To buy

9 boxes

65 tiles including 10% waste, 7 spare in the last box

The floor is 12 ft (3.66 m) by 10 ft (3.05 m), 120.0 sq ft (11.15 m²). One 24 in (610 mm) × 12 in (305 mm) tile with its joint covers 2.03 sq ft (0.189 m²), so the floor takes 59.1 tiles before waste and 65 after it. At 8 tiles per box that is 9 boxes.

The same floor in every pattern

Each row uses that pattern's usual waste allowance, so you can see what a diagonal or herringbone layout costs in extra tile before you commit to it.

Pattern	Waste	Tiles	Boxes
Straight (grid)	10%	65	9
Offset (brick, 1/3 or 1/2)	10%	65	9
Diagonal (45°)	15%	68	9
Herringbone or chevron	20%	71	9

How to use it

Measure the room at floor level, wall to wall, in the two directions. If the room is not a rectangle, work out its area with the square footage calculator first and split it into rectangles here, or add the rectangles' tile counts together. Measure one actual tile rather than trusting the label: a tile sold as 12 × 24 in is often 11¾ × 23½ in or 11⅞ × 23⅞ in, and the difference adds up over a large floor.

Enter the grout joint you intend to use, pick the layout, and put in the number of tiles in a box if you know it. The waste allowance changes with the pattern; overwrite it if your installer or the shop recommends a different figure. Everything updates as you type, and the switch at the top converts every field between feet and inches and metric without losing what you entered.

The method

This is arithmetic, not a model. Four steps:

Floor area = length × width.
Area per tile = (tile length + joint) × (tile width + joint). Each tile is responsible for its own face plus one joint along two of its sides, which is exactly how a tiled floor tessellates.
Tiles = floor area ÷ area per tile, multiplied by (1 + waste %), rounded up.
Boxes = tiles ÷ tiles per box, rounded up.

Rounding happens only at the end. Rounding the exact tile count up before adding waste would add a tile of phantom waste on every calculation; rounding it down would occasionally leave you one short.

A worked example

The default above: a floor 12 ft by 10 ft is 120 sq ft (11.15 m²). A 12 × 24 in tile with a 1/8 in joint occupies 12.125 × 24.125 in, which is 292.5 square inches or 2.03 sq ft. 120 ÷ 2.03 is 59.07 tiles to cover the floor exactly. Straight lay at 10% waste makes that 64.98, rounded up to 65 tiles. At 8 tiles per box that is 8.1 boxes, so 9 boxes, which leaves 7 spare tiles. The same floor in herringbone at 20% needs 71 tiles and still 9 boxes, but with only one spare. That thin margin is the kind of thing the pattern table is there to show.

Waste allowances by pattern

The percentages are rules of thumb used by tile shops and installers. Nobody has measured them in a way that applies to your room, so treat them as a starting point:

Straight (grid): 5–10%. Joints line up both ways. Cuts only where the field meets a wall.
Offset (brick, 1/3 or 1/2): 10%. The offcut from the end of one row can often start the next, so waste stays close to straight lay.
Diagonal (45°): 15%. Every edge piece is a triangle, and the offcut from one edge rarely fits anywhere else.
Herringbone or chevron: 15–25%. Angled cuts along every edge, and small rooms lose a larger share to them.

Waste is higher than these figures in small rooms, rooms with many corners, pipes and door frames, and with large-format tiles where a single broken or badly cut piece is a big fraction of the order. It is lower in a large open rectangle, where most tiles are never cut.

Tiles per 100 sq ft by size

Exact coverage with a 1/8 in (3 mm) joint and no waste. Useful for a quick sense check of a quote.

Tile size	Per 100 sq ft	Per 10 m²
4 × 4 in (100 × 100 mm)	846.3	910.9
3 × 6 in (75 × 150 mm)	752.3	809.8
6 × 6 in (150 × 150 mm)	383.8	413.2
12 × 12 in (300 × 300 mm)	97.9	105.4
12 × 24 in (300 × 600 mm)	49.2	53.0
18 × 18 in (450 × 450 mm)	43.8	47.2
24 × 24 in (600 × 600 mm)	24.7	26.6
8 × 48 in plank (200 × 1200 mm)	36.8	39.6

Where this stops being reliable

Irregular rooms. The calculation assumes a rectangle. An L-shaped room entered as its bounding rectangle over-orders; split it into rectangles instead.
Very large tiles in small rooms. When a room is only three or four tiles across, cuts dominate and offcuts are often too small to reuse. Real waste can be well above 20%. Plan the cuts with the tile layout calculator and count pieces by hand.
Mixed batches. Tiles from different production runs can differ visibly in shade and slightly in size. Buy the whole order, spares included, from one batch; the batch or shade code is printed on the box.
Patterns with more than one tile size. Versailles and other multi-size patterns need the manufacturer's own coverage figure per set.

For the grout to fill those joints, use the grout calculator.

Common questions

How much extra tile should I buy?

The usual allowance is 10% for a straight or offset layout, 15% for diagonal and 15 to 25% for herringbone. Go higher for a small or awkward room, where edge cuts are a bigger share of the floor, and for natural stone with colour variation you want to pick through. Keep a few spare tiles after the job: a matching batch is often impossible to find years later when one cracks.

Do I include the grout joint when working out tile quantities?

Yes, and this calculator does. Each tile covers its own face plus one joint in each direction. With large tiles the difference is small, about 1.5% for 12 × 24 in tiles with 1/8 in joints, but it grows as tiles shrink: about 6% for 4 × 4 in tiles at the same joint, and more with wider joints.

Why does the box count sometimes jump by one when I change the waste by a single percent?

Because both tiles and boxes are rounded up. If the exact figure is just under a whole box, one more percent of waste tips it over. It is worth seeing where the boundary is: if 10% needs 17 boxes and 9% needs 16, the choice is between one spare box and a very thin margin.

Should I subtract the area under a vanity or kitchen island?

Only if you are certain it will never move. Tiling under a freestanding vanity or appliance costs little and saves you from a gap if it is ever replaced with a different size. Built-in cabinets are usually installed on top of or up to the tile edge; subtract them if the plan is to tile around them.

My tile is sold by the square foot, not by the box. What do I enter?

Leave tiles per box empty and the calculator gives a tile count. Multiply that by the area of one tile to get the square footage to order. If the shop rounds up to whole boxes anyway, ask how many tiles a box holds and enter that for an exact box count.