How this calculator works. Tiles = (area × (1 + waste%)) ÷ tile face area, rounded up. Boxes = waste-adjusted area ÷ coverage per box (check your box label — 10–11 sq ft is typical for 12×24 tile, but it varies by product).
Waste factors follow standard tile-industry guidance: 10% for straight lay, 15% for diagonal or herringbone, 20% for rooms with many obstacles, alcoves, or large-format tile in small rooms.
How much tile do I need?
Tile is sold by the box, priced per square foot — so your real question is box count. Measure the room, add the waste factor, and divide by the coverage printed on the box you're buying. The waste factor isn't padding to skip: every edge row gets cut, every cut can break, and dye lots vary between production runs, so buying a second batch later risks a visible color shift.
Buy one extra box beyond the calculation and store it. Cracked tiles years from now are guaranteed; matching discontinued tile is nearly impossible. An attic box of your exact dye lot is the cheapest insurance in home improvement.
Waste factor by layout
| Layout | Add |
|---|---|
| Straight lay, simple room | 10% |
| Diagonal, herringbone, offset patterns | 15% |
| Many cuts: alcoves, curves, small room + large tile | 20% |
Buying tips
For walls, measure each wall separately (width × height), subtract only large openings like windows, and add the areas together before applying waste. For showers, waste runs high — use 15% minimum. And confirm all boxes at checkout show the same dye-lot number printed on the label.
Common questions
Do I subtract the grout lines?
No — grout joints are small enough that the standard practice is to ignore them, which builds in a tiny extra margin. The waste factor is what actually protects you.
How many 12×24 tiles per box?
Usually 5–8 tiles covering 10–11 sq ft, but it varies by brand and thickness. Use the box coverage in advanced settings once you've picked your tile.
What about thinset and grout?
Rough guide: one 50-lb bag of thinset per 40–50 sq ft with a 1/4" trowel (large tile needs a bigger trowel and more), and one 25-lb bag of grout per 100–200 sq ft depending on tile size and joint width. Our grout & thinset calculator computes both bags exactly.
Should I order online or in store?
Either — but always from a single dye lot, and over-order rather than re-order. Returns of full unopened boxes are usually free at big-box stores, making generous ordering low-risk.