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CalcMax

Tile Calculator

Range: 1 ft – 10,000 ft

Range: 1 ft – 10,000 ft

Range: 0.50 in – 200 in

Range: 0.50 in – 200 in

Range: 0 mm – 25 mm

Range: 0 – 50

Result

195

Tiles to buy

Surface area in square feet
180 ft²
Surface area in square metres
16.72 m²

Tile calculator: measure the floor or the wall you are tiling, give the size of one tile and the width of the grout joint, and it returns how many tiles to buy. The area is the easy half — length times width — and the two things that catch people are the joint and the rounding. A 300 mm tile does not cover 0.09 square metres: with a 3 mm joint it claims (303 × 303) = 0.0918 square metres, and that 2% is the difference between a plausible order and a second trip. Then the count is rounded up to whole tiles, because a tile is not sold by area — the last row along each wall is cut, and the off-cut from one end of the room rarely fits the other. The wastage allowance covers exactly that: 10% for a straight lay in a rectangular room, 15% for a diagonal or herringbone layout, a room with a lot of doorways, or anything you are cutting around. Tiles are not interchangeable either — the same nominal 300 by 600 is a different product at two suppliers, and a different batch of the same product can be a shade off, which is the argument for a spare box rather than for more arithmetic.

What one tile covers, at a 3 mm joint

Tile sizeCoverage per tile (ft²)Tiles per ft²Tiles per m²
100 × 100 mm (4 in)0.1148.7694.26
200 × 200 mm (8 in)0.4442.2524.27
300 × 300 mm (12 in)0.9881.0110.89
300 × 600 mm (12 × 24 in)1.9670.515.47
600 × 600 mm (24 in)3.9140.262.75
800 × 800 mm (32 in)6.9410.141.55

Every row is computed with a 3 mm joint, which is the reference this page uses and not necessarily yours: the same 800 mm tile covers 0.6432 square metres at a 2 mm joint and 0.648 at a 5 mm joint. Read the third and fourth columns as the fast estimate — multiply your area by them and round up — and read the first column as the reminder that the tile and the joint together are what covers the floor. These are nominal sizes: check the box, because a tile sold as 300 mm is often 298 mm and the joint is measured from the real edge.

Formula

Tiles = ceil( length × width × (1 + wastage ÷ 100) ÷ (tile length + joint) ÷ (tile width + joint) )

L
Length of the floor or wall being tiled, in feet
W
Width of the floor or wall, in feet
t
Length of one tile, in inches
u
Width of one tile, in inches
j
Width of the grout joint, in millimetres
w
Wastage allowance as a percentage of the tiled area

Use it once you have chosen the tile, because the size and the joint width are the two inputs that decide the answer, and neither can be read off the room. The joint is a decision rather than a measurement: a rectified porcelain tile can be laid with a 2 mm joint, a pressed ceramic usually wants 3 mm, and a thick-bed installation on an uneven floor can need 5 mm or more. A wider joint means each tile claims more of the floor and the room takes fewer tiles, which is why the joint is a field rather than a fixed 1/8 inch. Measure the finished floor area rather than the room: a room that is 3 metres wide with a 100 mm skirting on both sides has 2.8 metres of floor to tile, and a wall that includes a window has less than its full height.

Worked examples

  1. A 12 ft by 15 ft floor in 12 inch tiles, 3 mm joint

    1. Floor area: 12 × 15 = 180 square feet (16.72 m²)
    2. With 10% wastage: 180 × 1.10 = 198 square feet
    3. One 12 × 12 inch tile plus a 3 mm joint: 12.118 × 12.118 = 146.8 in² = 1.0198 ft²
    4. Tiles: 198 ÷ 1.0198 = 194.2, rounded up to 195 tiles

    These are the page defaults and the joint does almost nothing here — a 3 mm joint on a 12 inch tile makes each tile claim 2% more floor, which is 4 tiles fewer over this floor — 198 with no joint against 194.2 with one. Compare the next example, where the same 3 mm joint on a 24 inch tile claims only 1% more. The joint is a fixed width, so its effect shrinks as the tile gets bigger, which is the reason large-format tiles need a bigger allowance for the cuts rather than for the joints.

  2. A 20 ft by 18 ft floor in 24 inch tiles, 10% wastage

    1. Floor area: 20 × 18 = 360 square feet (33.45 m²)
    2. With 10% wastage: 360 × 1.10 = 396 square feet
    3. One 24 × 24 inch tile plus a 3 mm joint: 24.118² = 581.7 in² = 4.0395 ft²
    4. Tiles: 396 ÷ 4.0395 = 98.0, rounded up to 99 tiles

    99 is the round-up of 98.0 — the arithmetic lands almost exactly on a whole tile, so a slightly different joint or a slightly out-of-square room moves the answer by a whole tile. Large-format tiles are also where the wastage allowance earns its keep: a 24 inch tile cut for a 20 foot wall leaves a 20 inch off-cut that is useless anywhere else in the room, and a diagonal layout wastes considerably more.

  3. A small 10 ft by 12 ft floor in 12 by 24 inch tiles, 15% wastage

    1. Floor area: 10 × 12 = 120 square feet (11.15 m²)
    2. With 15% wastage: 120 × 1.15 = 138 square feet
    3. One 12 × 24 inch tile plus a 3 mm joint: 12.118 × 24.118 = 292.3 in² = 2.0296 ft²
    4. Tiles: 138 ÷ 2.0296 = 67.99, rounded up to 68 tiles

    Two thirds of the floor area of the first example and only a third of the tiles, because a 12 by 24 inch tile covers twice what a 12 by 12 does. A rectangular tile also has a direction: laid with the long side across a narrow room it wastes less, and laid the other way it wastes more, which is why the allowance matters more than the area on a room like this one.

Limitations

The arithmetic is exact; the joint and the wastage allowance are the assumptions. The joint is applied as one full joint on each side of every tile, which is one joint more per row than a room actually has — the missing half-joint lands where the last tile is cut anyway, and it is the same convention the paver calculator uses. A wider joint (thick-bed on an uneven floor, 5 mm or more) genuinely means fewer tiles, because the joint itself takes up part of the floor, and a rectified tile laid tight (2 mm) means slightly more. The wastage allowance is a flat percentage for a whole room, which is a crude way to account for the cuts along the walls and around the doorways: a plain rectangle with square tiles wastes the least, a diagonal or herringbone layout wastes more, and a small bathroom with a toilet, a basin and a pipe box wastes more still. Tiles are counted per piece, so the answer is never the bare area divided by the bare tile — a room 3 tiles wide and 4.4 tiles long needs 15 tiles for the last row, not 13.2. Not counted here: adhesive, grout, spacers, the leveling clips, the trim for the edges and the underlay or the uncoupling membrane. Finally, the tile sizes in the reference table are nominal: check the actual size on the box, because a 300 mm tile is often 298 mm, and the joint is measured from that.

Frequently asked questions

How many tiles do I need for a 12 by 15 foot room?
195 tiles in 12 inch squares with a 3 mm joint and 10% wastage: the floor is 180 square feet, the allowance takes it to 198, one tile plus its joint covers 1.0198 square feet, and 198 ÷ 1.0198 = 194.2, rounded up. Drop the joint to zero and the same floor takes 198 tiles; move up to 24 inch tiles and it takes 50. The tile size moves the answer far more than the room does.
How wide should a grout joint be?
Two millimetres for a rectified porcelain tile, which is cut square and can be laid tight; three millimetres for a pressed ceramic tile, which is not quite square and needs the joint to absorb the variation; five millimetres or more for thick-bed work on an uneven floor. Wider joints are more forgiving to lay and slightly fewer tiles to buy, because the joint is floor area of its own — and they are also the style choice: a wide joint reads as a deliberate grid.
Should I add wastage on top of the tile count?
Yes, and the figure belongs on the area rather than on the tile count. Ten percent is normal for a straight lay in a rectangular room, fifteen for a diagonal or herringbone layout, a room with several doorways or a lot of cutting around a basin and a toilet. Buy the spare box and keep it unopened: tiles are made in batches, and a tile from a different batch can be a shade off the one you laid.
Why does the calculator count a joint on every side of the tile?
Because it is the simplest convention that matches the tiling trade: a row of n tiles has n − 1 joints between them, so counting n joints over-counts by half a joint — and that half joint falls exactly where the last tile is cut for the wall, where the off-cut is bigger than the error anyway. The paver calculator uses the same rule, so the same tile gives the same coverage in both tools.
Does this work for wall tiles as well as floor tiles?
Yes, the arithmetic is identical — only the measurement changes. For a wall, measure the finished tiled area rather than the full wall: a window, a shower screen or a tiled splashback ends the tile line, and a wall that is tiled only above a bath is less than its full height. Wall tiles are usually smaller and thinner than floor tiles, so the joint matters proportionally more: a 100 mm tile with a 3 mm joint is 6% bigger than the tile alone.
What else do I need to buy besides tiles?
Adhesive and grout, both of which are bought by area or by weight rather than by the tile; spacers or the leveling clips, which are counted per joint; trim for the edges and the corners; and an uncoupling membrane or a backer board if the floor is going over timber or underfloor heating. None of them are counted on this page, and the tile count is the one number you can be sure of before you have them.

References

Related calculators

Flooring CalculatorFlooring needed for a room, with waste allowance.Paver CalculatorPavers, sand and base gravel for a patio or path.Square Footage CalculatorSquare footage of a room or an irregular floor plan.Paint CalculatorPaint needed for a room, deducting doors and windows.