THE MATH, MADE VISIBLE
How it works
Add the net areas that will receive the same tile. Each tile occupies its face size plus one grout joint in each direction: footprint = (tile length + joint) × (tile width + joint). Tiles = round up(net area × (1 + allowance ÷ 100) ÷ footprint). Boxes = round up(tiles ÷ tiles per box). Cost = whole boxes × your price per box.
Real project examples
A bathroom floor
10 × 8 ft = 80 ft². With 12 × 12 in tile and a 1/8 in joint, each tile occupies about 1.021 ft². Add 10%: 88 ft² ÷ 1.021 ft² = 86.2, so plan 87 tiles. At 10 tiles per box, buy 9 boxes (90 tiles). At $30 per box, material cost is $270.
A backsplash in two runs
10 × 1.5 ft plus 4 × 1.5 ft = 21 ft². With 3 × 6 in subway tile, a 1/16 in joint and 10% extra, plan 180 tiles. At 40 tiles per box, buy 5 boxes (200 tiles).
Before you buy
- Enter the actual tile dimensions from the carton or specification sheet. The nominal size in a product name can differ slightly from the measured size.
- Tile manufacturers publish a recommended minimum grout joint for each product, and rectified tile can allow a narrower joint than other edges. Use the joint your product and installer call for; it is a planning input here, not a recommendation.
- The 10% allowance is an editable planning assumption for cuts and breakage. Diagonal, herringbone and other cut-heavy layouts often need more; ask your installer for a figure for your layout.
- Daltile recommends buying roughly 10% extra as “attic stock” for future repairs. Decide whether your allowance is for cutting only or for cutting plus spares, and raise it if you want both.
- Buy every box from the same production lot where the product lists one, and check return rules for unopened boxes before you order extra.
- This estimate covers field tile only. Trim pieces, mortar, grout, backer board and waterproofing are separate products with their own coverage.
Questions worth asking
Why does the grout joint change the tile count?
Each tile covers its own face plus a share of the joints around it. A 12 × 12 in tile with a 1/8 in joint occupies about 1.021 ft², so the bathroom example needs 87 tiles rather than the 88 you get by ignoring joints. The effect is small for large tiles and larger for small tiles with wide joints.
How do I exclude a vanity, tub or cabinet?
If your installation plan leaves that area untiled, enter its footprint as Excluded area for that area. It is subtracted before the allowance is applied.
Does this calculate grout or thinset?
No. Grout depends on joint width, tile thickness and tile size, and mortar on trowel size and substrate. Use the coverage information for the products you buy.
Can I combine the floor and the walls in one estimate?
Only if they use the same tile and box. A different size or product has its own footprint and box count, so estimate it separately.
Sources & assumptions
NIST · unit conversion factorsDaltile · FAQs, including attic stockDaltile · grout joint recommendations when selecting tileLast reviewed October 1, 2026. Planning defaults are editable examples. Product labels and supplier information override them.