Tile Calculator · Practical guide
How Much Extra Tile Should I Buy for Waste?
The 10-15% rule explained, with exact overage numbers for real project sizes.
At a glance
The Short Answer
Buy 10% more tile than your measured area needs for a standard straight layout, 15% for diagonal or patterned layouts, and up to 20% for complex patterns or large-format tiles. On a 100 sq ft floor with 12x12 tiles, that means ordering 110, 115, or 120 tiles respectively.
Interactive tool
Tile Calculator
Enter your own values, then compare the result with the examples below.
Tile Estimate
Wastage by Layout Type
| Layout | Recommended Waste | Tiles for 100 Sq Ft (12x12) |
|---|---|---|
| Straight (grid) | 10% | 110 |
| Brick / running bond | 10-12% | 110-112 |
| Diagonal (45 degrees) | 15% | 115 |
| Herringbone / chevron | 15-20% | 115-120 |
Where the Waste Actually Goes
- Edge cuts: every wall, doorway, and corner requires partial tiles, and the offcuts rarely fit anywhere else.
- Breakage: tiles crack during cutting, handling, and setting — plan on losing a few.
- Future repairs: a cracked tile years from now can only be fixed invisibly if you kept spares from the same batch.
When to Go Above 15%
Rooms with many obstacles (kitchen islands, bathroom vanities, angled walls) generate more cuts per square foot than open rectangles. Very large tiles waste more per cut, and natural stone varies enough that you may cull some pieces. In those cases 15-20% is cheap insurance — running short mid-job risks a dye-lot mismatch that no amount of savings justifies.
Enter your wastage percentage in the calculator above and it adds the buffer to your tile count automatically.
Frequently Asked Questions
Is 10% waste enough for a simple square room?
Usually yes for a straight grid layout with 12x12 tiles. If the room dimensions are not an even multiple of the tile size, or you are a first-time installer, bump it to 12-15%.
Can I return unused tiles?
Most big-box stores accept returns of full, unopened boxes within a set window, which makes over-buying low-risk. Keep your receipt and check the store's policy before purchasing.
Does the grout gap reduce how many tiles I need?
Slightly — each tile plus its grout gap covers a bit more area. The calculator already adds your grout gap to the tile dimensions, so the count it gives accounts for that effect.
How many spare tiles should I keep after the job?
Keep at least 3-5 full tiles, or one full box for larger projects. Tile lines are frequently discontinued, and matching color and texture years later is often impossible.