How the tile calculator works
Most free calculators divide the area by the tile size and add ten percent. That ignores the grout joint, the laying pattern and anything in the wall that will not be tiled. Stukko does the sum the way a tiler does it on paper.
- Net area. Length × width (or the area you type in), minus every door, window and fixture you add.
- Effective tile size. Tile length plus joint, times tile width plus joint. A 600 × 300 mm tile with a 2 mm joint takes up 602 × 302 mm.
- Tiles before waste. Net area divided by the effective tile area.
- Waste. A percentage that depends on the pattern: 10 % for a straight grid, 12 % for brick bond, 15 % for diagonal or herringbone. You can override it.
- Round up. To whole tiles, then to whole boxes if you enter tiles per box.
Adhesive and grout are optional. Adhesive is bag weight divided by the coverage printed on the bag, times the net area. Grout uses the standard trade formula: (length + width) ÷ (length × width) × joint width × tile thickness × density, which gives kilograms per square metre for your exact tile and joint. Both carry their own 10 % allowance, separate from the tile waste: adhesive beds vary with the substrate and some grout always stays in the bucket.
Measuring the room
Measure the longest length and the widest width of the floor in metres. For an L-shaped room, split it into two rectangles, calculate each one and add the tile counts, or add the areas and use the “total area” option. For walls, measure the width and the height to be tiled, not the full wall height if you are only tiling to dado level.
Openings are entered as width × height with a count, so two identical windows are one line. Anything smaller than a tile, such as a socket, is not worth subtracting.
Choosing the waste allowance
The waste defaults are trade rules of thumb. A first-time tiler laying a diagonal pattern in a room with alcoves should push the waste up to 20 %. Rectified large-format tiles laid in a straight grid on a plain rectangle can get away with 5 %. Buying a spare box is always cheaper than a second delivery of tiles from a different batch with a slightly different shade.
Switching units
Use the metric/imperial toggle if your tiles are sold in inches or your room is measured in feet. Every value converts in place and the result is the same within one tile, because the calculation is always done in metres behind the scenes.