Tile measuring guide & FAQs
The whole-box formula
First multiply the measured tile area by (1 + your extra allowance ÷ 100). Then divide the adjusted result by the square feet stated on the box. Always round UP to the next whole carton. This is independent of the tile piece estimate, which uses the individual tile face size.
Example: 120 square feet, 10% extra
A 120-square-foot room requires 132 square feet after a 10% allowance. Tile sold in boxes marked 15 square feet each calls for 9 whole boxes, providing 135 square feet of labeled coverage. If the price is $45 per box, tile material cost would be $405 before any optional taxes.
Before you place the order
Confirm that the manufacturer’s packaging coverage matches your chosen finish, and avoid mixing different lots where appearance may vary. Ask about returns for unopened cartons, and keep a small quantity of matching tiles for future repairs if feasible.
Frequently asked questions
Why round the number of boxes up?
Stores commonly sell tile by the full carton. If an order needs 8.8 boxes, you cannot normally buy 0.8 of a carton, so the tool rounds to nine full boxes.
What should I enter for square feet per box?
Use the coverage shown on the exact tile product packaging or its product listing; do not assume every box covers 15 square feet.
How accurate is this tile calculator?
The measured area and box rounding follow explicit formulas. Tile cuts, uneven walls, product sizes, coverage labels and installation methods can change the actual amount needed, so use the result as a purchase-planning estimate.
Method & sources: The formulas are documented in our methodology. Reference guidance: Home Depot — how to lay tile and backsplash measurements. Retail guidance is informational, not a partnership or endorsement. Updated Nov 3, 2026.