How to calculate how many tiles you need
Every tile count starts with the area. Measure each surface, multiply length by width for a floor or width by height for a wall, and subtract the parts that stay bare, like a window or the space behind a tub. Then work out how much room one tile takes. Tiles never sit edge to edge: each one takes its own size plus one grout joint in both directions. Divide the area by that and round up.
Example: a 10 × 12 ft bathroom floor is 120 square feet. A 12 × 12 inch tile with a 1/8-inch joint takes up 12.125 × 12.125 = 147.02 square inches, or 1.021 square feet. 120 ÷ 1.021 = 117.5, so the floor needs 118 tiles. With 10 percent waste for a straight layout that becomes 130 tiles, and at 15 tiles per box you buy 9 boxes.
Tiles per 100 square feet
| Tile size | Tiles per sq ft | 100 sq ft | +10% straight | +15% diagonal |
|---|---|---|---|---|
| 3 × 6 in subway | 7.52 | 753 | 828 | 866 |
| 4 × 4 in | 8.46 | 847 | 931 | 974 |
| 6 × 24 in plank | 0.97 | 98 | 108 | 113 |
| 12 × 12 in | 0.98 | 98 | 108 | 113 |
| 12 × 24 in | 0.49 | 50 | 55 | 57 |
| 24 × 24 in | 0.25 | 25 | 28 | 29 |
All rows use 1/8-inch grout joints and are rounded up. Subway tile on a wall is often set with 1/16-inch joints, which makes it 776 tiles per 100 square feet instead of 753.
Waste by layout pattern
- Straight or brick pattern: about 10 percent is typical.
- Diagonal: about 15 percent is typical, since every tile along the walls is cut at an angle.
- Herringbone or chevron: 15 to 20 percent is typical. The calculator uses 20 percent to stay on the safe side.
- Custom: enter your own percentage, for example 5 percent for a plain rectangle, or more for large tiles in a small room.
Waste covers cuts at the edges, broken tiles and the odd mistake. Keep the leftovers: a few spare tiles make it easy to replace a cracked one years later, when the same color lot is no longer sold.
Floor, wall, backsplash and shower
Add one area for each surface. A floor takes length × width; a wall, a backsplash or a shower wall takes width × height. Use the How many field for walls of the same size, and the Subtract type for a window, a door or a tub. For example, a 60-inch tub surround has a 5 ft back wall and two 2.5 ft end walls, tiled 6 ft high: (5 + 2.5 + 2.5) × 6 = 60 square feet. With 12 × 24 inch tile and 1/8-inch joints that is 30 tiles, or 33 with 10 percent waste.
Typical grout joint widths are 1/16 inch for rectified tile and wall subway tile, 1/8 inch for most floor tile and 3/16 to 1/4 inch for handmade or uneven tile. The joint width the tile maker recommends on the box comes first. For the tile cost, enter a price per tile, per box or per square foot. When you price by the square foot and enter a box size, the cost counts the full boxes you buy, since stores sell whole boxes.
How to use the tile calculator
- 1Choose US units or metric, then add one row per surface: floor, wall, backsplash or shower wall. Enter its size, and add a Subtract row for a window or a tub.
- 2Type the tile size or tap a common size, and pick the grout joint that matches the spacers you plan to use.
- 3Pick the layout pattern to set the waste: straight, diagonal, herringbone or a custom percentage.
- 4Enter the tiles or square feet per box from the box label to see how many boxes to buy.
- 5Optionally enter a price per tile, box or square foot for the cost, then copy the result or the link for your trip to the tile store.
Frequently asked questions
How many tiles do I need for 100 square feet?
With 12 × 12 inch tiles and 1/8-inch grout joints, each tile takes up about 1.02 square feet, so 100 square feet needs 98 tiles. Add 10 percent waste for a straight layout and buy 108. Larger 12 × 24 tiles need 50 (55 with waste) and 24 × 24 tiles need 25 (28 with waste).
How much extra tile should I buy for waste?
Typical allowances are 10 percent for a straight or brick pattern, 15 percent for a diagonal layout and 15 to 20 percent for herringbone, because angled layouts need a cut tile at every wall. Small rooms, many corners and large tiles push the waste up. Keep a few spare tiles after the job for repairs, since a later batch may not match in color.
Does the grout joint width change how many tiles I need?
Yes, because every joint adds to the space each tile takes up. For 100 square feet of 12 × 12 tile you need 99 tiles with 1/16-inch joints and 96 with 1/4-inch joints. Small tiles show a bigger difference: 3 × 6 subway tile takes 776 tiles with 1/16-inch joints but 709 with 1/4-inch joints.
How many subway tiles do I need for a backsplash?
Measure the width of each wall section and the height from the countertop to the upper cabinets, often about 18 inches (1.5 ft). A backsplash of 20 ft by 1.5 ft is 30 square feet. With 3 × 6 subway tile and 1/16-inch joints that is 233 tiles, or 256 with 10 percent waste. Subtract a window if the tile stops at its edges.
How many boxes of tile do I need?
Divide the number of tiles including waste by the tiles per box on the label and round up. If the box lists its coverage instead, divide the area plus waste by the square feet per box: 132 square feet ÷ 15.5 square feet per box is 8.5, so buy 9 boxes. Buy all boxes at once and check that they share the same lot number, so the color matches.