gizmobench

Tile Calculator

Add each surface you are tiling, take off the doorways and hearths, give the tile's face size and the grout joint you are using, and read back four numbers instead of one: the area, the tiles the bare area needs, the tiles your waste allowance adds, and the boxes to buy. The grout gap is a real input here, because it changes the answer: one square metre of 100 mm tiles is 100 tiles edge to edge and 93 once a 4 mm joint is counted. The waste percentage stays yours and stays visible, rather than being folded invisibly into a total, and the tile can be measured in one unit while the room is measured in another.

Tiles to buy0tilesType a width and a height to start, in feet.
Net area
0 sq ft
Tiles for the area
0
Waste adds
0
Total tiles
0
Boxes
0

Areas to tile

One line per surface: a floor, a wall, a splashback. Measure the full rectangle and take the doorways off below. Press Enter in any field to add another line.

Measured in
Gross area
0 sq ft
Openings off
0 sq ft
  • not yet

Openings to take off

A doorway, a hearth, a shower tray, a window in a tiled wall. Each one comes off the gross area before the tiles are counted.

The tile and the joint

The face size is the tile itself, without the joint. The grout gap is the spacer you are using: 3 mm is a common floor joint, and a 1/8 inch spacer is 3.175 mm.

Tile measured in

Waste and boxes

The waste allowance is yours: the field opens at 10 percent, and whatever you type is what gets added. The tiles it adds are counted separately on the readout above, so you can always see the two numbers apart.

Worked examples

Each one runs through the same function as your own numbers. Load one to see it in the fields.

  • A 10 by 10 ft floor1 ft tiles, no joint, no waste
    100 sq ft · 100 tiles · 10 boxes
  • A 3.2 by 2.4 m kitchen floor600 by 600 mm tiles, 3 mm joint, 10 percent waste, 4 per box
    7.68 m² · 25 tiles · 7 boxes
  • A 2.4 by 2.4 m wall, less the door300 by 600 mm tiles, 2 mm joint, 10 percent waste, 8 per box
    4.16 m² · 26 tiles · 4 boxes
Quantity, not method. Exact arithmetic on the dimensions you enter: area, the tile count with the grout joint included, and boxes rounded up. It cannot know your layout pattern or the offcuts a particular room forces, so the waste percentage is an allowance you set, and the box count is the number to buy from. It counts tiles for an area and stops there: nothing here sizes a substrate, an adhesive or a floor.

Common questions

How much waste should I allow, and why is 10 percent the usual figure?
Ten percent is the figure most tile suppliers and fitters start from for a straight layout in a plain rectangular room, and the waste field on this page opens at 10 for that reason. A diagonal or herringbone layout cuts more tiles at every edge, so people commonly allow more, and a room full of alcoves cuts more again. The page has no view of its own: whatever you type is what it adds, it is rounded up to whole tiles, and the tiles it adds are shown as their own number. A 100-tile floor at 10 percent comes out as 100 plus 10, which is 110 tiles.
Does the grout gap really change how many tiles I need?
Yes, and by more than most people expect on a small tile. A tile in a continuous field carries the joint on two of its four edges, so the gap is added once to the tile's width and once to its height. A 100 mm tile with a 4 mm joint occupies 104 mm by 104 mm, which is about 8 percent more surface each. One square metre goes from 100 tiles to 93. On a 600 mm tile the same joint barely moves the count, which is why the gap is a field you set rather than a figure baked into the answer.
How do I handle a doorway, a hearth or a shower tray?
Measure the whole rectangle as an area, then add the doorway or hearth in the openings group underneath. Each opening is taken off the gross area before any tile is counted, and the readout shows the gross area and the openings separately so you can check the subtraction. If the openings add up to more than the area itself, the page says so and names both figures rather than printing a negative area or a count of zero.
Why is the box count rounded up, and what do I do with the offcuts?
Because a supplier sells whole boxes. At 10 tiles a box, 101 tiles is 11 boxes, not 10.1, and the eleventh box is the one that gets you finished. The spare tiles are worth keeping: a cracked tile two years from now is almost never matched by a new batch, since colour and size drift between production runs. Fitters also mix tiles from several boxes as they lay them, which evens out any shade difference between boxes.
Can I measure the room in feet and the tile in millimetres?
Yes. The room and the tile have their own unit controls, and both sides are converted through the exact definitions, where an inch is 0.0254 metres and a foot is 0.3048 metres. That matters because a quote often gives a room in feet and a tile in millimetres. A 10 by 10 foot floor with 1 foot tiles, no joint and no waste, comes out at exactly 100 tiles, and the same floor described in metres, centimetres, millimetres or inches gives the same 100.
Does it tell me how to lay the tiles out or where the cuts fall?
No, and that is deliberate. This page divides an area by the surface one tile plus its joint takes up and rounds up: it is a count, not a plan. Where the cuts land depends on where you start the first row, whether you are running a brick bond or a herringbone, and how square the room is. That is what the waste allowance is for, and it is also why the page counts material only and says nothing about the substrate, the adhesive or the floor underneath.

Exact arithmetic on the dimensions you enter: area, the tile count with the grout joint included, and boxes rounded up. It cannot know your layout pattern or the offcuts a particular room forces, so the waste percentage is an allowance you set, and the box count is the number to buy from.