Number Tile Calculator
Tiles by the room, not by guesswork. Enter the floor, pick a tile size (or type your own), set the grout gap, and get the tile count two independent ways — by coverage and by the actual grid — plus boxes and cost with the standard 10% waste allowance built in.
How it works
Two methods, cross-checked. By coverage: room area ÷ one tile’s area, rounded up, then +10% for cuts and breakage. By grid: tiles along each wall = room side (in inches) ÷ (tile size + grout gap), rounded up per side, then multiplied — the count if you lay whole tiles and cut only at the edges. When the grid count is higher it is usually the honest one for small rooms and big tiles. Boxes round up from the coverage count, because stores sell whole boxes.
Formula & worked example
Formula: By coverage: room area ÷ one tile’s area, rounded up. By grid: each wall’s length in inches ÷ (tile size + grout gap), rounded up per side, then multiplied. Buy the coverage count plus a waste allowance (10% standard): ceil(count × 1.10), then divide by tiles per box and round up again.
Worked example: A 10 × 12 ft room (120 sq ft) with 12 × 12 in tiles: 120 tiles by coverage, and the grid with a 1/8 in grout gap agrees at 120 (10 across × 12 down). With 10% waste you buy 132 tiles — 14 boxes of 10, about $630 at $45 a box.
When to use this
- You are retiling a bathroom floor and the tile you want is a large plank, not the square tile every rough guide assumes.
- A store associate gave you a box count from area alone and you want the grid count as a second opinion.
- You are comparing a subway tile against a large-format tile for the same wall and the box counts are not directly comparable.
- You are ordering online, where one box short means a week of waiting and a possible dye-lot change.
How to use it, step by step
- Enter the room length and width in feet.
- Pick the tile size preset, or switch to custom and type the tile dimensions in inches.
- Set the grout gap you will actually lay — the preset jobs on the page run at 1/8 inch.
- Enter tiles per box and the box cost from the product you are buying.
- Compare the coverage count against the grid count, then buy the waste-adjusted total in whole boxes.
What the inputs mean
| Input | What it is | Typical values |
|---|---|---|
| Room length and width | The surface being tiled, in feet | Bathroom floors commonly 40 to 90 sq ft |
| Tile size | Preset or custom tile dimensions in inches | 3 by 6 subway up to 24 by 24; 12 by 24 plank in the example below |
| Grout gap | Joint width added to each tile in the grid count | 0.125 in (1/8) is the page default |
| Tiles per box | Count printed on the carton | 10 is the page default; large planks often ship fewer |
| Cost per box | Shelf price for one carton | $45 is the page default |
Another worked example
An 8 by 9 ft bathroom floor is 72 sq ft. With 12 by 24 in plank tiles and a 1/8 in grout gap, the coverage count is 36 tiles, but the grid count is 40 — 8 across by 5 down — because each row and column rounds up on its own. The buy count with 10% waste is also 40 tiles: 5 boxes of 8, costing $260 at $52 a box. When the two methods disagree, this is the size of room where the gap shows up.
Frequently asked questions
How many tiles for a 10 × 12 ft room with 12-inch tiles?
The room is 120 sq ft and each 12 × 12 tile covers exactly 1 sq ft, so 120 tiles by coverage. Add the standard 10% waste allowance and you buy 132 tiles — 14 boxes of 10, about $630 at $45 a box. The grid method with a 1/8-inch grout gap also lands on 120 before waste (10 across × 12 down).
Why does the grid count differ from the coverage count?
Coverage assumes tiles can be cut and pieces reused anywhere; the grid counts whole tiles per row and column with grout gaps, rounding up on each side. Big tiles in small rooms make the grid count jump — a half-tile strip on two walls still consumes whole tiles unless offcuts fit elsewhere.
How much waste should I add?
10% for straight layouts in rectangular rooms, 15% for diagonal or large-format tile, 20% for herringbone and rooms with many corners. Breakage in transit and cutting mistakes are normal, and dye lots differ — running short mid-job is the expensive outcome.
Does the grout gap really change the count?
A little. Each tile effectively occupies tile size + gap, so a 12-inch tile on 1/8-inch grout covers a 12.125-inch module. On long walls that quietly removes a tile per row now and then — the grid count above includes it, the coverage count does not.
🪨 Tiling the patio too?
The Gravel Calculator works out cubic yards, tons and bags for the base layer underneath.
Can I use this for a backsplash or shower wall?
Yes — enter the wall's width and height as the length and width. The count works the same on a flat vertical rectangle. Measure niches, benches and the wall above a tub surround separately and add those tiles on top, because a single rectangle will not see them.
Should a small bathroom use large tiles?
It can, and it means fewer grout lines to clean, but check the grid count before falling in love: large tiles in a small room force a cut strip on most rows, so the grid count runs well past the coverage count and the waste share climbs. The waste allowance here is fixed at 10% — on a very cut-up small room, round your box order up one more box yourself.