Tile Calculator

Last updated October 7, 2026 · How we calculate

How to calculate how many tiles you need

Each tile covers its own face plus half of the grout joint around it, so the real coverage of one tile is a little bigger than the tile itself. The calculator adds the joint width to each side of the tile, divides your area by that coverage, then adds waste and rounds up to whole tiles and boxes.

Worked example: an 8 × 10 ft bathroom floor with 12 × 12 tile

1. Area: 8 × 10 = 80 sq ft.
2. Coverage per tile with a 1/8 in. joint: 12.125 × 12.125 = 147.02 sq in. ÷ 144 = 1.021 sq ft.
3. Tiles before waste: 80 ÷ 1.021 = 78.4, round up to 79 tiles.
4. Add 10% waste: 80 × 1.10 = 88 sq ft ÷ 1.021 = 86.2, round up to 87 tiles.
5. Boxes holding 10 sq ft (ten 12 × 12 tiles): 87 ÷ 10 = 8.7, round up to 9 boxes.

The joint makes a bigger difference with small tile. On the same 80 sq ft floor, 4 × 4 tile with no joint would take 720 pieces, but with 1/8 in. joints each tile covers 4.125 × 4.125 = 17.02 sq in., so you need 80 ÷ 0.1182 = 677.0, or 678 tiles before waste.

Tiles per 100 square feet by size

Counts below use the nominal size and a 1/8 in. grout joint, before waste. Add 10–15% for the number to buy.

How much extra tile to buy

Waste covers cuts along the walls, notches around toilet flanges and door jambs, breakage, and tiles you reject for chips or warping. Keep at least a few spare tiles after the job; matching discontinued tile later is often impossible.

Nominal vs. actual tile size

Tile is named by its nominal size, and the actual size can be slightly smaller. A "12 × 12" tile may actually measure a bit under 12 in., and a "12 × 24" might be 11.8 × 23.6 in. The difference is small per tile but adds up over a big floor. For the most accurate count, measure a tile or check the actual dimensions on the box, choose Custom size, and enter those numbers. Rectified tile is ground to precise, consistent dimensions, which is why it can be set with narrower joints.

Thinset and grout: rough planning notes

• Thinset coverage depends on the trowel. Larger tiles need a larger notch and more mortar, so a 50 lb bag covers far less floor under large-format tile than under small tile. Use the coverage chart printed on the bag for your trowel size.
• Get full contact. Industry standards call for at least 80% mortar coverage under floor tile in dry areas and 95% in showers and other wet areas. Pull up a tile now and then to check, and back-butter large tiles.
• Grout amount varies a lot. It depends on joint width, tile thickness and tile size; small tile with wide joints uses far more grout per square foot than large tile with narrow joints. Use the grout manufacturer's coverage chart.
• Sanded or unsanded: sanded grout is generally used for joints 1/8 in. and wider and unsanded grout for narrower joints. Some glass and polished stone call for unsanded or specialty grout to avoid scratching.
• The right backer: floors over wood subfloors usually get cement backer board or an uncoupling membrane. Shower walls need a waterproofed backer, not regular drywall.

Measuring tips

• For floors, measure wall to wall. You can skip the area under a vanity or cabinet base if you are not tiling under it.
• For walls and backsplashes, enter the wall length and the height you are tiling. Subtract large windows, but not outlets.
• For L-shaped or irregular spaces, total the area with our square footage calculator and use the total mode.
• Covering the rest of the house in plank flooring? The flooring calculator handles multiple rooms and box counts. Finishing new walls? See the drywall calculator and paint calculator.

Frequently asked questions