The Daltile tile FAQ recommends approximately 10% extra as attic stock for future replacement. That is a repair-spare recommendation. It should not silently be treated as the cutting waste for every layout.
Keep three quantities separate
Start with measured coverage area. Add a cutting allowance for the layout and room shape. Then decide whether to keep attic stock from the same batch. A diagonal or herringbone pattern can create different offcuts from a straight grid, so the correct allowance depends on the plan and the tile size.
The worksheet formula is:
Purchase area = measured area × (1 + cutting allowance ÷ 100) × (1 + repair reserve ÷ 100).
For the chosen 120 square feet, 10% cutting allowance and 10% reserve, 120 × 1.10 × 1.10 = 145.2 square feet. Applying 20% once would produce 144 square feet, which is slightly lower because two separate percentages compound. Choose one documented method and use it consistently.
Convert area to boxes
Read the coverage printed on the actual box. Suppose a chosen box covers 15 square feet. The 145.2 square foot planning quantity requires 145.2 ÷ 15 = 9.68 boxes, so round up to 10 full boxes, covering 150 square feet. The 4.8 square feet left after the order is not a guaranteed usable reserve because cuts and defects vary.
The box coverage and 15 square feet are illustrative inputs. Do not copy them to a product without checking its label. Tile sizes, grout joints, pattern repeats and box counts can change the coverage.
Compare layout scenarios
These scenarios hold the chosen 120 square foot area and 15 square foot box coverage constant. The percentages are planning inputs to discuss with the installer or supplier.
| Cutting allowance | Repair reserve | Planning area | Boxes at 15 sq ft/box |
|---|---|---|---|
| 5% | 0% | 126.0 sq ft | 9 |
| 10% | 0% | 132.0 sq ft | 9 |
| 10% | 10% | 145.2 sq ft | 10 |
| 15% | 10% | 151.8 sq ft | 11 |
The table does not declare that 5%, 10% or 15% is correct for your room. It shows the consequence of the choice. Keep the layout drawing, tile dimensions and box coverage beside the order.
Measure the room and obstacles
Measure each rectangular section and add them. Subtract areas that will not receive tile only when their boundaries are clear. Doorways, columns, angled walls and built-in cabinets can change the cutting pattern even when they barely change the total area.
If the room is not rectangular, divide it into simple shapes. Measure the longest dimensions and check them against the drawing. A small area error repeated across a large order can affect the number of boxes more than a rounding choice.
Keep the batch information
Buy enough from one dye lot when possible and save labeled spare tiles. Daltile explains that future batches can vary and describes attic stock as additional tile kept for later replacement. Store boxes where they remain dry and follow the manufacturer's handling instructions.
The estimate excludes grout, thin-set, trim, shipping damage, color variation and installation labor. It does not guarantee that a tile will be available later. A complex or structural installation needs an experienced installer; this guide does not give cutting or electrical instructions.
Use the flooring tile calculator for its supported rectangular inputs, then add documented layout and reserve decisions. Read paint and flooring measurements, room and furniture measuring and the vaulted-ceiling paint guide for related measurement context. The final order remains a planning estimate until the product box and layout are confirmed.
Review the order before purchase
Put the room sketch, tile dimensions, box coverage, pattern direction and allowance decision on one page. Check whether the supplier sells full boxes and whether a return policy applies to unopened material. A box count rounded up for area can still be wrong if the layout creates narrow cuts or a pattern repeat.
Ask the installer or supplier to review stairs, thresholds, transitions, drains, niches and any diagonal layout. Keep a labeled spare box after installation when storage allows. The calculation helps you explain the quantity decision, while the actual product label and layout determine the order. Do not use an area estimate as installation instructions.