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Tile Calculator

Calculators · Added

Measure the room, choose the tile, and this works out how many tiles to order and how many boxes that is. It accounts for the grout joint — a 600 mm tile with a 3 mm gap actually occupies 603 mm of floor — takes off doorways and windows, adds a cutting allowance you control, and rounds up to whole boxes the way a merchant does.

m
m

Openings to subtract — a doorway on a floor, a window or a shower tray on a wall. Optional.

mm
mm
mm

0 for rectified tiles butted together.

%

10% suits a straight lay in a square room.

0 if you are buying loose.

Optional. Price per tile if you set boxes to 0.

Choosing a wastage allowance

Straight lay, square room — 10%
The usual starting point for a rectangular floor with few cuts.
Straight lay, awkward room — 15%
Alcoves, a bay window, pipe boxing — anything that multiplies the cut edges.
Diagonal or herringbone — 20%
Every perimeter tile is a cut, and the offcuts rarely serve twice.
Large-format tiles — 15%
A cut in a 600 × 1200 tile wastes more surface than a cut in a 300 × 300 one.

These are trade rules of thumb rather than a standard. The right figure depends on the room, the tile and who is laying it — ask your tiler what they work to.

How to use the tile calculator

  1. 1Pick the unit your measurements are in, then enter the width and length of the area. Add more areas if the job covers several rooms or walls.
  2. 2Add any openings that will not be tiled — a doorway, a window, a shower tray — and they come off the total.
  3. 3Choose a tile size from the list or type your own, and set the grout joint. Use 0 for rectified tiles butted together.
  4. 4Set a cutting allowance. Ten per cent suits a straight lay in a square room; a diagonal or herringbone pattern needs closer to twenty.
  5. 5Enter how many tiles come in a box, and a price if you want the order costed. Set boxes to 0 if you are buying loose.

Examples

A 4 m by 3 m floor in 600 mm tiles

Input
12 m², 600 × 600 mm tiles, 3 mm joint, 10% wastage, 4 per box
Result
34 tiles bare, 38 to buy, 10 boxes

Six spare tiles at the end, which is the right number to keep for repairs.

The same floor with no grout joint

Input
12 m², 600 × 600 mm tiles, 0 mm joint
Result
34 tiles bare

A 3 mm joint on a 600 mm tile changes the count by about 1%. On a 100 mm mosaic it changes it by 6%.

A bathroom wall with a window

Input
4 m × 2.5 m wall, less a 1 m × 1 m window, 200 mm tiles
Result
9 m² to tile, 225 tiles

The opening comes off before the tile count, not after.

Imperial measurements

Input
10 ft × 10 ft, 12 inch tiles, no joint
Result
100 tiles

Feet and inches are converted to metres internally; the area is reported both ways.

About the tile calculator

What the number actually means

The bare requirement is the area you measured divided by the area one tile occupies with its joint, rounded up. It assumes every cut is perfect and every offcut is usable, which is why it is a floor rather than an estimate: nobody has ever tiled a room with exactly that many tiles.

The cutting allowance is what turns it into an order. It covers the offcuts that end up in the skip, the tile that breaks while being scored, and the one that comes out of the box already chipped. Setting it yourself rather than having a fixed figure buried in the code is deliberate — the right number depends on the room and the pattern, and hiding it would be guessing on your behalf.

Boxes, not tiles, are what you buy

Tile is sold by the box, and a box always rounds up. Ordering 38 tiles when a box holds four means ten boxes and 40 tiles, so the real spare is six rather than the four the allowance suggested. That gap is reported here rather than hidden, because it changes what you should do at the end of the job.

Coverage per box is sometimes quoted in square metres rather than as a tile count. If that is all you have, divide the box coverage by the area of one tile to get the count — and check whether the merchant's coverage figure already includes a grout joint, because some do and some do not.

Measuring an awkward room

Rooms are rarely simple rectangles. The reliable approach is to break the floor into rectangles that do meet at right angles, measure each, and add them as separate areas here. An L-shaped room is two rectangles; a room with a chimney breast is one rectangle with a small deduction.

Measure at floor level rather than at waist height, because skirting, plaster and old walls all lean. And measure both ends of each wall: if they differ, use the larger figure, since the tiles have to cross the widest part and the surplus becomes a cut rather than a shortfall.

Frequently asked questions

Why does adding grout reduce the number of tiles?
Because the joint is part of the surface. Each tile plus its joint occupies more floor than the tile alone, so fewer of them are needed to reach the same area. It is a small effect on large-format tiles and a substantial one on small ones: a 3 mm joint costs a 600 mm tile about one per cent of its coverage and a 100 mm mosaic about six.
How much wastage should I allow?
Ten per cent is the usual starting point for a straight lay in a rectangular room. Push it to fifteen if the room has alcoves, a bay or pipe boxing, and to twenty for a diagonal or herringbone pattern where every perimeter tile is a cut and the offcuts rarely serve twice. Large-format tiles also waste more, because a cut in a 600 × 1200 tile throws away more surface than a cut in a small one.
Should I order extra beyond the allowance?
Keep whatever the boxes leave you with. Tiles are made in batches and the colour drifts between them, so a replacement bought in two years will rarely match what is on your floor — the spare tiles from the original order are the only ones guaranteed to. A box under the stairs is cheap insurance against one chipped tile becoming a re-tiled room.
Does this account for the pattern I want to lay?
Only through the wastage figure. The count here is area-based, so it tells you what to order rather than how to set the job out. A pattern that has to line up across a threshold, a brick bond with a specific offset, or a border in a second tile all need a setting-out drawing, and the tile count that comes out of one can be higher than the area suggests.
Can I use it for a wall as well as a floor?
Yes — measure the wall width and its height instead of the room width and length, and deduct the window or the shower tray as an opening. The arithmetic is identical. What differs is practical: wall tiles are usually smaller, joints are usually wider, and the top row is nearly always a cut, so the allowance is better set at the higher end.

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