Tile and Flooring Calculator: Boxes and Waste
Tile and Flooring Calculator
Floor or wall area to boxes, with a waste allowance and the individual tile count for planning cuts. Enter the room in metres or feet and the box coverage as printed on the carton.
Waste allowance covers cuts, breakage and the spare box every tiler wants for future repairs: 10 percent is the usual starting point for a straight lay in a square room, 15 percent where the room is irregular or the tile is large, and 20 percent or more for a diagonal or herringbone pattern, where offcuts rarely serve twice. Dye lots vary between production runs, so the spare box is best bought with the job, not a year later.
How to use this tool
Room length and width, a waste percentage, and the coverage printed on the box: out comes the number of boxes to buy, the coverage that actually gets you, and the individual tile count if you enter a tile size. An optional price per box gives a running cost.
Waste is not padding, it is the cuts
Every tile that meets a wall gets cut, and the offcut usually cannot be used elsewhere. That is the bulk of the waste allowance: 10 percent for a straight lay in a squarish room, 15 percent where the room is irregular or the tile is large, and 20 percent or more for diagonal and herringbone patterns where nearly every perimeter tile is a bespoke cut and the offcuts are triangles nobody can reuse.
The other reason for the allowance is the spare box. Dye lots differ between production runs, so a tile bought next year to replace a cracked one will not quite match. The box left in the garage is cheap insurance, and it is one of the few cases where over-ordering is the correct decision rather than a mistake.
A worked check you can repeat on paper
A 5 by 4 metre room is 20 square metres. Adding 10 percent waste gives 22 square metres to buy. At 1.5 square metres per box that is 14.67 boxes, so 15 boxes, delivering 22.5 square metres. In 300 by 600 millimetre tiles, each covering 0.18 square metres, the 22 square metres is about 122 tiles. Every one of those roundings goes up, because two thirds of a box is not a purchasable quantity.
Mistakes that catch people out
Ordering the measured area. Twenty square metres of tile does not tile a twenty square metre room. Fix: the waste box, never zero.
Forgetting the pattern. A diagonal lay in a 10 percent estimate runs out. Fix: raise the waste to 20 percent for diagonal or herringbone.
Measuring the room but tiling the alcove too. Bay windows, hearths and thresholds are extra area. Fix: add them in, or measure the tiled footprint rather than the room.
Rounding boxes down because it is close. Fourteen point seven boxes is fifteen boxes. Fix: the tool always rounds up, and an exact fit is left alone.
How this was checked
The worked example above was verified end to end, and the rounding behaviour was tested at the boundary specifically: exactly 15 square metres at 1.5 per box returns 10 boxes with no spare, while 15.01 square metres returns 11. The tile count was cross-checked against the tile footprint for the 300 by 600 case.
Related Calculators and Reference
Irregular rooms are easier measured in pieces with the 2D Area Calculator. Painting the same room is the Paint Coverage Calculator, and comparing tile prices across box sizes is the Unit Price Comparison Calculator. Rooms getting carpet instead are the Carpet Calculator, which lays whole strips off the roll. Venting the steam from a bathroom is the Bathroom Fan CFM Calculator.