How Much Tile Do I Need?

How do you calculate square feet for tile?

Measure the length and width of the area in feet and multiply them. A floor 12 feet long and 10 feet wide is 12 × 10 = 120 square feet. Convert inches to decimal feet first, so 10 feet 6 inches is 10.5 feet. The square footage calculator handles this and mixed units, and our guide on how to calculate square footage covers other room shapes.

Split an L-shaped room into rectangles, work out each one, and add them. A 12 × 10 ft room with an 8 × 5 ft alcove is 120 + 40 = 160 square feet. For a wall, multiply the width by the height you plan to tile, then subtract large openings such as windows and doors.

Don't subtract small obstacles such as a toilet flange or floor vent. You still have to cut tile around them, and the offcuts rarely get used elsewhere.

How many tiles per square foot do you need?

Tiles per square foot = 144 ÷ (tile length × tile width), with both tile dimensions in inches. There are 144 square inches in a square foot, so a 6 × 6-inch tile covers 36 square inches, and 144 ÷ 36 = 4 tiles per square foot.

The table gives the no-joint figure from that formula, followed by the counts our tile calculator returns for a 120-square-foot room with 1/8-inch joints. The last column adds 10% for cuts and breakage.

What is the tile estimate formula?

Tiles = area in square inches ÷ ((tile length + joint) × (tile width + joint)), rounded up. Each tile effectively covers its own face plus one joint width in each direction, which is why the joint belongs in the formula.

Worked example: a 12 × 10 ft floor with 12 × 12-inch tile and 1/8-inch joints.

• Area: 12 × 10 = 120 square feet, which is 120 × 144 = 17,280 square inches.
• Space per tile: 12.125 × 12.125 = 147.02 square inches.
• Tiles: 17,280 ÷ 147.02 = 117.54, which rounds up to 118.
• With 10% extra: 117.54 × 1.10 = 129.29, which rounds up to 130.
• Boxes of 10: 130 ÷ 10 = 13 boxes.

How do grout joints change the tile count?

Wider grout joints reduce the number of tiles, because each joint adds to the area a tile takes up. The change is small for large tile and much bigger for small tile. Going from no joint to a 1/4-inch joint in our 120-square-foot room saves 4 of 120 tiles with 12 × 12-inch tile, but 123 of 1,080 with 4 × 4-inch tile.

A grout joint is the filled gap between tiles. Follow the tile manufacturer's recommendation for its width, not just the look you want. The ANSI A108 installation standards set a 1/16-inch minimum, and trade guidance ties the joint to the tile's actual size variation, so a narrow joint isn't suitable for every tile or floor. Tile Letter, a trade publication, explains how flatness, tile tolerances and movement all limit how narrow a joint can go.

Tile sizes are also usually nominal, meaning a tile sold as 12 × 12 may measure slightly less. For a large or tightly budgeted job, measure a real tile and enter that size.

How much extra tile should you buy?

A common rule of thumb is 10% extra for a straight layout, and 15% or more for diagonal or herringbone patterns. These are trade rules of thumb that vary from source to source. We did not find a published standard that sets them, so use them as a starting point and defer to your installer or the tile maker.

Waste comes from cuts at walls and around obstacles, breakage in handling, and tiles rejected for chips or shade. Diagonal layouts waste more because every edge tile gets cut at an angle. Small rooms also tend to run higher, because a larger share of the tiles touch a wall.

The table applies each allowance to the worked example, 117.54 tiles of 12 × 12-inch tile in boxes of 10. Our calculator shows the 10% line; the others are our own arithmetic using the same method.

How do you work out how many boxes of tile to buy?

Divide the tiles needed, including waste, by the tiles per box and round up. Tile is usually sold by the full box, so 130 tiles at 10 per box is 13 boxes, and 131 tiles would be 14.

Check the label, because box quantities vary by product and many list coverage in square feet as well as a tile count. If it gives only coverage, divide your area with waste by the coverage per box. For 120 square feet plus 10%, or 132 square feet, in boxes covering 15 square feet, that is 132 ÷ 15 = 8.8, so 9 boxes.

For an L-shaped 160-square-foot room with the same tile and joint, the tile calculator returns 157 tiles, or 173 with 10% extra. That is 16 boxes of 10, or 18 with the extra.

What else should you check before ordering tile?

Confirm a few practical points before you place the order, since they can change the amount you need or the finished result.

• Buy from one production lot where possible, because shade can differ between lots. Lot numbers are usually printed on the box.
• Keep a few spare tiles for future repairs. A discontinued tile can be hard to match later.
• Dry-lay a row to see where cuts will fall. A slim sliver at one wall may mean shifting the layout, which can use more tile.
• Ask about returns on unopened boxes before you decide how much extra to carry.
• Budget separately for thinset, grout, spacers and any backer board, which this estimate doesn't cover.