Tile Calculator
Buy this many
9 boxes
132 tiles including the 10% cutting allowance, and boxes of 15 do not divide evenly into that.
- Tiles needed
- 132
- Tiles in that many boxes
- 135
- Spare tiles left over
- 3
- Each tile covers
- 1 sq ft
Keep the spares. Tile is made in batches that vary slightly in colour, so a replacement bought in two years will not match — the leftovers from your own box are the only exact match you will ever have.
How this is calculated
Tile involves two roundings, one after the other, and the second is the one that catches people. First the area divides by the size of a tile to give a tile count, and a cutting allowance goes on top because tiles at the edges get cut and the offcuts are rarely usable elsewhere. Then that tile count divides by however many come in a box, and rounds up again, because nobody sells a third of a box. Those two roundings compound: a job needing 132 tiles in boxes of fifteen is nine boxes, which is 135 tiles, so three spare. The cutting allowance is where judgement comes in. Ten percent is the usual figure for a simple rectangular room laid straight. Fifteen is more realistic for a room with alcoves, or any diagonal or herringbone layout, where almost every edge tile is a cut and the offcut angles rarely repeat. Large-format tiles want more than small ones, because a bad cut wastes more.
Worked example
A twelve-inch tile covers exactly one square foot, so 120 square feet is 120 tiles before cuts, and 132 with ten percent added. Boxes of fifteen mean eight boxes gives 120 tiles, which is not enough, so nine boxes it is — 135 tiles, and three left over. Those three are worth more than they look.
Inputs: 120 square feet, 12 by 12 inch tiles, 15 to a box, 10% for cuts
Result: 9 boxes — 132 tiles needed, 135 in the boxes, 3 spare
What this assumes
- The cutting allowance covers edges and breakages, not layout waste: a diagonal or herringbone pattern wants fifteen percent or more, not ten.
- Tiles are rectangular and laid in a straight grid. A pattern mixing sizes needs each size worked out separately.
- Box counts vary by size and manufacturer. Check the box rather than assuming, because it changes the answer more than anything else here.
Questions
- How much extra should I allow for cuts?
- Ten percent for a plain rectangular room laid square, fifteen for anything with alcoves or a diagonal or herringbone layout, and more again for large-format tiles where a bad cut wastes a lot of tile. If you are learning as you go, allow the higher figure — running out mid-floor is worse than a spare box.
- Why does it tell me how many spares I will have?
- Because they are the most valuable tiles you will own. Tile is fired in batches and colour varies between them, so a replacement bought in two years will not quite match. If one cracks, the only exact match is a tile from your own original box. Keep them somewhere dry and do not use them up on offcuts.
- Can I return the boxes I do not open?
- Usually, and that is worth asking before you buy rather than after. Many suppliers take back full, unopened boxes within a window, which makes rounding up considerably less painful — but almost none take back a box you opened to get at three tiles.
- What will the tile cost?
- Type the price of a box and the result card costs the boxes this page tells you to buy, waste allowance and round-up included. Tile is only sold by the box, so costing anything else would be costing a purchase you cannot make. The price is yours, never ours, because tile prices vary enormously by range and retailer.