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Tile Calculator: Tiles, Boxes, Thinset and Grout
Find out how many tiles you need for a floor, shower wall or backsplash, based on tile size and grout joint, plus how much thinset and grout to buy.
How many tiles do I need?
Divide the area you are tiling by the area one tile covers, including its share of the grout joint, then add waste for cuts. For a 12 × 24 in tile with a 1/8 in joint, each tile covers (12.125 × 24.125) ÷ 144 = 2.03 sq ft. An 8 × 6 ft bathroom floor (48 sq ft) needs 48 ÷ 2.03 = 24 tiles, or 26 with 10% waste.
How much waste to allow
Use 10% for a standard straight layout, 15% for diagonal or herringbone patterns, and more for large tiles in small rooms where each cut wastes a big piece. It's worth keeping a few spare tiles for future repairs.
Thinset and grout
A 50 lb bag of thinset covers about 90 to 100 sq ft with the 1/4 × 1/4 in square-notch trowel used for small tile, about 70 sq ft with a 1/4 × 3/8 in trowel for 8 to 15 in tile, and about 45 to 50 sq ft with the 1/2 in trowel needed for large-format tile. The calculator picks the trowel from your tile size.
Grout depends on joint width, tile size and thickness: small tiles with wide joints use far more grout. We use the formula grout (lb) = area × (L + W) × joint × thickness × 9.9 ÷ (L × W), with 10% extra. Check the coverage chart on your grout bag, since densities vary by product.
Tips
- Buy all tile from the same lot number so the color matches.
- Wall tile in a shower: measure each wall separately and add them, then subtract any niche or window.
- Large tiles (15 in and up) need a flat floor; they show every bump.
Frequently asked questions
How many 12x24 tiles do I need for 100 square feet?
Each 12 × 24 in tile with a 1/8 in joint covers about 2.03 sq ft, so 100 sq ft takes about 50 tiles, or 55 with 10% waste.
How many square feet does a bag of thinset cover?
A 50 lb bag covers roughly 90 to 100 sq ft with a 1/4 in square-notch trowel, and about 45 to 50 sq ft with the 1/2 in trowel used for large tiles.