# How many tiles do I need?

Computes how many tiles cover a floor or wall from its size, the tile size, and the grout gap, with an extra share for cuts and breakage, and the boxes to buy.

- Page: https://www.acalculator.org/construction/tile-calculator
- JSON spec: https://www.acalculator.org/construction/tile-calculator.json
- Version: 48b834769872

## Default answer

Example with the default inputs (Area length 12 ft, Area width 10 ft, Tile length 12 in, Tile width 12 in, Grout gap 0.125 in, Extra for waste 10%): For 120 ft², buy 130 tiles (129.29 before rounding up).

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| l | Area length | The length of the floor or wall to tile. |
| w | Area width | The width of the floor, or the height of the wall. |
| tl | Tile length | The length of one tile. |
| tw | Tile width | The width of one tile. |
| g | Grout gap | The width of the grout joint between tiles; 0 for none. |
| extra | Extra for waste | Tile to add, in percent, for cuts, breakage, and spares: about 10% for a straight layout, 15% for diagonal or herringbone. |
| box | Tiles per box | How many tiles come in one box, from the label; leave empty to skip boxes. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| tiles | Tiles to buy | The area with extra ÷ the area each tile covers with its grout, rounded up to whole tiles. |
| exactTiles | Tiles, not rounded | The area with extra ÷ the area each tile covers, before rounding up. |
| noExtra | Tiles with no extra | The area ÷ the area each tile covers, rounded up, with no extra for waste. |
| boxes | Boxes to buy | The tiles to buy ÷ the tiles per box, rounded up. |
| squareFeet | Area, ft² | The area to tile in square feet, before the extra. |
| squareMeters | Area, m² | The area to tile in square metres, before the extra. |

## Method

tiles = length × width × (1 + extra ÷ 100) ÷ ((tile length + gap) × (tile width + gap)), rounded up; boxes = tiles ÷ tiles per box, rounded up.

## Assumptions

- The area is a rectangle. Split an L-shaped room into rectangles and add the tiles.
- Each tile covers its own size plus one grout gap in each direction.
- Extra for waste is 10% by default (Daltile: about 10% more); use about 15% for diagonal, herringbone, or large tiles (Arizona Tile: 10% to 15%).
- Tiles are counted by area; the count does not plan where cuts fall.

## Worked examples

1. l = 3.6576, w = 3.048, tl = 0.3048, tw = 0.3048, g = 0, extra = 10% gives squareFeet = 120, exactTiles = 132, tiles = 132, noExtra = 120. Source: Daltile, Tile & Stone FAQs: buy about 10% more tile than you need (https://www.daltile.com/how-to/faqs).
2. l = 3.6576, w = 3.048, tl = 0.3048, tw = 0.3048, g = 0.003175, extra = 10%, box = 15 gives exactTiles = 129.29238, tiles = 130, noExtra = 118, boxes = 9. Source: Daltile, Tile & Stone FAQs: buy about 10% more tile (https://www.daltile.com/how-to/faqs).
3. l = 3, w = 2.4, tl = 0.3, tw = 0.6, g = 0.003, extra = 15% gives squareMeters = 7.2, exactTiles = 45.317965, tiles = 46. Source: Arizona Tile, How Much Extra Tile To Buy: 10% to 15% extra (https://www.arizonatile.com/how-much-extra-tile-to-buy/).

## FAQ

### How do I calculate how many tiles I need?

Multiply the length by the width to get the area. Add the grout gap to each side of one tile and multiply those to get the area one tile covers. Divide, add about 10% for waste, and round up. A 12 × 10 ft floor of 12 in tiles with 1/8 in grout needs 130 tiles.

### How much extra tile should I buy?

About 10% for a straight layout, which Daltile recommends. Tile sellers such as Arizona Tile suggest 10% to 15%; use the high end for diagonal or herringbone layouts, large tiles, and rooms with many corners, because those need more cuts.

### Does the grout gap change the tile count?

Yes, a little. Each tile covers its own size plus one gap in each direction. With 12 in tiles and a 1/8 in gap, a tile covers 12.125 × 12.125 in, so a floor needs about 2% fewer tiles than with no gap.

### How do I tile an L-shaped room?

Split it into rectangles, enter each one, and add the tile counts. Round each part up, or add the unrounded counts and round once to buy a little less.

### How many square feet does a box of tile cover?

The box label gives it, usually as square feet per box. This calculator counts tiles, so enter the tiles per box from the label to get the boxes to buy.

### Should I keep spare tiles?

Yes. A few spare tiles from the same batch let you replace a cracked tile later; a new batch can differ in color. The extra for waste usually leaves some.

## Sources

- Daltile, Tile & Stone FAQs (attic stock: buy approximately 10% more tile than you need), retrieved 2026-10-01. https://www.daltile.com/how-to/faqs
- Arizona Tile, How Much Extra Tile To Buy? (10% to 15% additional tile), retrieved 2026-10-01. https://www.arizonatile.com/how-much-extra-tile-to-buy/
- NIST SP 811 (2008), Appendix B.8: 1 in = 0.0254 m and 1 ft = 0.3048 m exactly, retrieved 2026-10-01. https://www.nist.gov/pml/special-publication-811