Tile Calculator

How to use this tile calculator

1. Measure each area you’re tiling. Floors go wall to wall. For walls and showers, use the width and the height the tile will reach. Enter rectangles, and a triangle for an angled corner.
2. Enter the tile size as it’s sold, such as 12 × 24 inches, and the grout joint, which is the size of your spacers.
3. Choose a layout. Straight and brick layouts waste the least. Diagonal and herringbone layouts end in angled cuts at every wall.
4. Enter how much one box covers. It’s on the box and the product page.
5. Pick your trowel notch so the calculator can count bags of thinset.

The result gives the number of tiles and boxes, bags of thinset, and pounds of grout. The cost uses example prices you can change.

How the calculator works

tiles   = area × (1 + extra) ÷ area of one tile plus its joint, rounded up
boxes   = tiles × tile area ÷ box coverage, rounded up
thinset = area ÷ coverage per 50 lb bag, rounded up
grout   = area × J × D × (L + W + J) ÷ ((L + J) × (W + J)) × 9.33 lb
          (L, W = tile size, J = joint width, D = tile thickness, all in inches)

Each tile covers its own face plus half the joint on every side, so a 12-inch tile with 1/8 inch joints takes up 1.02 square feet, not 1. The count uses that bigger number, then turns tiles back into square feet to count boxes.

The extra pays for cuts at the walls, around the toilet flange and door jambs, and the tile that cracks on the saw. Fireclay Tile recommends at least 15% for field tile and 20% for herringbone, parquet, and specialty shapes. Fireclay’s tile is handmade, and a later order may not match the color. For machine-made tile in a simple room, we start at 10% for straight and brick layouts and 15% for diagonal ones. Those two are our estimates. Herringbone uses Fireclay’s 20%.

Thinset coverage comes from CUSTOM Building Products’ data sheets. VersaBond covers 85 to 95 square feet per 50-pound bag with a 1/4 × 1/4 inch square notch and 60 to 67 with a 1/4 × 3/8 inch notch. VersaBond-LFT, the large-format version, covers 42 to 47 with a 1/2 inch notch or a 3/4 inch U-notch held at 30 degrees. We use the low number, because CUSTOM requires mortar under at least 80% of each tile in dry areas and 95% in wet ones.

Grout is our own formula. It finds the volume of the joints around each tile and multiplies by a density of 112 pounds per cubic foot, which is where the 9.33 comes from (112 ÷ 12). CUSTOM publishes coverage charts rather than a formula, and this one matches its Polyblend Plus charts within about 6% for tiles 4 inches and larger. For small mosaics it errs toward more grout.

A worked example

Say you’re tiling an 8 × 10 bathroom floor with 12 × 24 inch porcelain tile, 1/8 inch joints, and a straight layout. Each box covers 16 square feet, and you’re using a large-format trowel.

• Area: 8 × 10 = 80 square feet, plus 10% = 88 square feet
• One tile with its joint: 12.125 × 24.125 = 292.5 square inches, or 2.03 square feet
• Tiles: 88 ÷ 2.03 = 43.3, so 44 tiles
• Boxes: 44 tiles × 2 square feet = 88 square feet ÷ 16 = 5.5, so 6 boxes, with about 4 tiles to spare
• Thinset: 80 ÷ 42 = 1.9, so 2 bags of 50 pounds
• Grout: about 4.3 pounds of sanded grout, so one small box

Grout for common tile sizes

Pounds of grout for 100 square feet, with 1/4 inch thick tile up to 6 inches and 3/8 inch thick tile above that:

Joint width matters more than most people expect. Going from 1/8 to 1/4 inch roughly doubles the grout for any tile size.

Tips for buying and setting tile

• Buy every box at once and check that the lot numbers match. Shade can shift from one production run to the next.
• Keep a few spare tiles after the job. A cracked tile is easy to replace when you have a match on the shelf.
• Dry-lay a row before you mix any thinset. Starting from the center line usually leaves cuts of the same size at both walls.
• Lift a freshly set tile now and then to check the back is covered. Back-butter large tiles if the coverage is patchy.
• Wait the full cure time before grouting. CUSTOM calls for 24 hours with VersaBond.
• Tile in a shower goes over cement backer board or a waterproofing membrane, not plain drywall. The drywall calculator covers the rest of the bathroom walls, and the flooring calculator handles rooms getting planks instead of tile.