Tile calculator by tile size

Tile questions

How many tiles do I need per square foot?

Divide 144 by the area one tile covers in square inches, joint included. A 12 × 12 tile with a 1/8 in joint covers about 147 sq in, so just under one tile per square foot; a 3 × 6 subway tile with a 1/16 in joint covers about 18.6 sq in, so about 7.75 tiles per square foot. Then add waste.

How much extra tile should I buy?

About 10% for a straight or offset layout, 15% for a diagonal layout and 20% for herringbone, which has the most cuts. Small rooms with many corners and rooms with planks run higher. Keep a few spare tiles after the job for repairs.

Does the grout joint change the tile count?

A little. Each tile takes up its own face plus half a joint on every side, so wider joints mean slightly fewer tiles. On a 12 × 12 tile the difference between a 1/16 in and a 1/4 in joint is about 3%.

How much thinset and grout will I use?

A 50 lb bag of thinset covers roughly 75–95 sq ft with a 1/4 × 1/4 in square-notch trowel, and roughly 40–50 sq ft with the 1/2 in notch that large-format tile needs. Grout depends on the joint volume — tile size, joint width and tile thickness — so small tiles and mosaics use far more than large tiles. The calculator shows both; the bag's own chart is the final word.

Do I need a permit to retile a shower?

Retiling in place often doesn't. Rebuilding the shower — a new pan, moving the drain or the valve — involves plumbing, which is permitted and inspected work. We tell you which applies before we start.