Tile Calculator

This is an estimate, not professional advice. Check your inputs and verify the result against your plans and local building code before you build or order. See terms and disclaimer.

How this calculator works

Enter your dimensions and the result updates instantly. A waste allowance is included so you order slightly over rather than running short mid-pour, and ready-mix is rounded up to the nearest quarter yard, which is how it is sold.

Worked example

A 10 ft × 10 ft floor with 12 × 12 in tiles, 1/8 in joints and a 10% waste allowance. Inputs: Area length 10 ft, Area width 10 ft, Tile length 12 in, Tile width 12 in, Waste allowance 10 %, Grout joint width 0.125 in, Tile thickness 0.375 in, Thinset coverage per 50 lb bag 95 ft². Result: 110 .

Tiles for common floor sizes

Calculated for 12 × 12 in tiles with a 10% waste allowance. Tap a size to load it in the calculator above.

Method & assumptions

The number of tiles is the area you are covering divided by the face of one tile. One square foot is 144 square inches, so a tile that measures L by W inches covers (L times W) divided by 144 square feet. We take your area, add the waste allowance for cuts and breakage, divide by that tile face and round up, because you cannot buy part of a tile. A 12 by 12 inch tile covers exactly one square foot, so 100 square feet plus 10% waste needs 110 tiles.

Thinset mortar is the adhesive bed under the tile, and its coverage depends almost entirely on the notched trowel, not the tile count. A 1/4 inch square-notch trowel spreads a 50 lb bag over roughly 95 square feet, a 1/4 by 3/8 inch trowel over about 70, and a 1/2 inch trowel for large-format tile over only 40 to 50 (Mapei and TEC coverage charts). We divide your bare area by the coverage you pick and round up. Back-buttering large tiles, an uneven substrate or an uncoupling membrane all lower coverage, so treat the bag count as a floor, not a ceiling.

Grout fills the joints between tiles, and the amount follows the TCNA method: grout in pounds equals (tile length plus width) divided by (length times width), times the joint width, times the joint depth, times a density constant of about 8.25, times the area. Smaller tiles and wider joints mean far more grout, because there is more linear joint per square foot. Tile thickness sets the joint depth, since joints are filled to the full depth of the tile under ANSI A108.10. For a plain square-footage job with no tiles, use our square footage calculator, and for boxed plank flooring see the flooring calculator.

Pro tips and common mistakes

• Buy 10 to 20% extra and keep spares. Add 10% waste for a straight lay, 15% for a diagonal and 20% for herringbone or a room full of cuts. Order it all in one lot so the shade matches, and set aside a few full tiles for future repairs, since dye lots drift between runs.
• Match the trowel to the tile. A 1/4 inch trowel suits mosaics and small tile; 12 inch and larger tile needs a 1/4 by 3/8 or 1/2 inch trowel and much more thinset per square foot. The wrong trowel leaves voids that crack tiles later.
• Back-butter large-format tile. Tiles 15 inches or longer on any side should be back-buttered for full coverage, which the TCNA recommends at 95% in wet areas. This uses noticeably more thinset than the chart, so round the bags up.
• Pick sanded or unsanded grout by joint. Use sanded grout for joints 1/8 inch and wider, and unsanded for joints under 1/8 inch or with polished stone that sand can scratch. Wider joints need more grout, so set the joint width honestly.
• Do not forget the substrate. Tiles are only as sound as what is under them. Budget for backer board or an uncoupling membrane, plus edge trim, spacers and a sealer for cement grout. These are not in the tile count above.

Frequently asked questions

References

• Tile Council of North America (TCNA)
• ANSI A108/A118 tile installation standards
• Tile (Wikipedia)

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