ReckonBoxCounting tiles without a second trip to the store
The number of tiles you need is the area to cover divided by the area of one tile. A 120 square foot floor with 12 by 24 inch tiles, each 2 square feet, comes to 60 tiles before anything is cut.
Then reality intrudes. Tiles crack, cuts at the wall leave unusable offcuts, and a shade that matches today is discontinued next spring. So the order is not 60, it is 66 once you add 10 percent, and since tile sells by the box, 66 tiles at 8 per box rounds up to 9 boxes. That rounding is where a bare tile count quietly betrays you: 8.25 boxes is still 9 boxes at the register.
Waste follows the pattern, not a fixed number
A straight grid layout wastes about 10 percent of the tile, and a diagonal or herringbone pattern wastes 15 to 20 percent. The angle is the reason. Lay tile square to the walls and most cuts happen only at the edges. Turn it 45 degrees and every border tile is a triangle, with the cut-off corner too small to reuse anywhere.
This tool sets the floor by the layout you pick: 10 percent for straight, 20 percent for diagonal. Enter a higher number and it uses yours, since a room full of tight corners or a busy mosaic can eat more. The point is that copying a flat 10 percent onto a herringbone job is how people end up short with the pattern half-laid.
| 120 sq ft floor, 12x24 tiles | Straight | Diagonal |
|---|---|---|
| Tiles for the bare area | 60 | 60 |
| Waste factor | 10% | 20% |
| Tiles to order | 66 | 72 |
| Boxes at 8 per box | 9 | 9 |
One tile in square feet
Tile is sold by the inch and floors are measured by the foot, so the two have to meet. Multiply the tile width by its height in inches and divide by 144, because a square foot holds 144 square inches. A 12 by 24 inch tile is 288 square inches, or 2 square feet. A 4 by 4 inch mosaic is 16 square inches, about 0.111 square feet, which is why an 18 square foot backsplash swallows 162 of them.
Where the numbers come from
Area comes from length times width in feet. Tile area converts from inches with the divide-by-144 step. Dividing the two gives the bare tile count, the waste factor scales it up, and dividing by tiles per box and rounding up gives boxes. If you enter a price per box, the cost is on the whole boxes you actually carry out, not the fractional count. Everything rounds up at the box, because half a box does not exist.
What this does not cover
This estimates field tile for a rectangular area with a uniform waste factor. It does not lay out the pattern to minimize cuts, place the border and accent tiles, or size the trim and bullnose pieces along an exposed edge. It also treats the grout gap as absorbed by the waste factor, which holds for a normal joint but not for a wide-grout or large-format job where you would add the gap to each tile. The estimate is the quantity, not the plan.
Buy from one production run and keep the leftover box, because the tile you match by eye two years later never quite matches.
Frequently asked questions
How many tiles do I need? Divide the area to cover by the area of one tile. A 120 square foot floor with 12 by 24 inch tiles, each 2 square feet, needs 60 tiles before waste. Add 10% for a straight lay and you order 66 tiles, which at 8 tiles per box is 9 boxes. Always round boxes up, since you buy whole boxes.
How much waste should I add for tile? Add 10% for a straight grid layout and 15% to 20% for a diagonal or herringbone pattern, where more tiles get cut at an angle and the offcuts are unusable. This tool sets a 10% floor for a straight lay and a 20% floor for a diagonal one, so the order already reflects the pattern you choose. Keeping a few spares also helps for future repairs.
How do I find the area of one tile in square feet? Multiply the tile width by its height in inches, then divide by 144, since a square foot is 144 square inches. A 12 by 24 inch tile is 288 square inches, or 2 square feet. A 4 by 4 inch tile is 16 square inches, about 0.111 square feet, which is why a small backsplash still takes a lot of them.
How many boxes of tile is that? Divide the tiles you need by the tiles per box and round up. Boxes hold anywhere from 6 large tiles to 90 small mosaic pieces, so the count on the box matters. For 66 tiles at 8 per box, that is 8.25 boxes, which rounds to 9. Buying by the box from one production run also keeps the color and shade consistent.
Should I measure the grout gap? For most floor and wall tile the grout gap is small enough that dividing area by tile size, then adding a waste factor, covers it. The gap slightly reduces how many tiles fit, which the waste allowance absorbs. For a precise large-format or thin-grout job you can add the gap to each tile dimension, but for a typical layout the area method with waste is close.