Quick answer: Buy about 10% extra for straight or grid layouts and 15% extra for diagonal, herringbone, or chevron patterns. Go to 15–20% for natural stone, small mosaics, complex rooms, or a first DIY install. The extra covers edge cuts, breakage, and future repairs.
Buying the exact number of tiles almost always backfires. This guide explains what eats into your count, the standard percentages, and when to go higher — so you order once and get it right.
Why you need extra tile
Four things consume tile beyond the basic area calculation:
- Edge and corner cuts: perimeter tiles rarely land on a full tile, and a tile cut to fit often wastes the offcut.
- Breakage: even with a wet saw, tiles snap. Porcelain is especially unforgiving, and first-timers break more.
- Defects: a box may hold a chipped, warped, or off-color tile that gets set aside.
- Future repairs: matching tile from the same lot years later is nearly impossible, so spares are valuable.
Recommended waste by layout
| Layout pattern | Waste % | Why |
|---|---|---|
| Straight / grid | 10% | Edge cuts along two walls only |
| Running bond / brick | 10% | Offset is predictable |
| Diagonal (45°) | 15% | Triangular cuts at all four walls |
| Herringbone | 15% | Many angled cuts; higher breakage |
| Chevron | 15% | Precision cuts at every joint |
Why 10% became the standard
On a 100 sq ft room, 10% adds 10 sq ft — roughly two rows of 12×12 tiles along two walls, usually enough to absorb cuts and a few breaks. It stuck because it balances the cost of running short (disruptive, and the new stock may not match) against the cost of overbuying.
When to go higher than 15%
- Complex room shapes: L-shaped or angled rooms need more cuts — see how to calculate tiles for a floor.
- Natural stone: marble, travertine, and slate vary in size and chip more easily.
- Very small tiles: mosaic sheets have high border-cut waste.
- Showers and niches: lots of cuts around fixtures — see how to calculate shower tile.
- First-time DIY: expect more breakage; add 15–20%.
Worked examples
Diagonal layout, same room: 100 base + 15% = 115 tiles
Waste is always rounded up, and then the total rounds up again to full boxes — so the real-world cushion is usually a little larger than the percentage suggests.
Frequently asked questions
- How much extra tile should I buy?
- Add about 10% for straight or grid layouts and 15% for diagonal, herringbone, or chevron patterns. Increase to 15-20% for natural stone, small mosaics, complex room shapes, or first-time DIY installs.
- Why is 10% the standard waste allowance?
- Ten percent balances two risks: running short mid-install, which is disruptive and may leave you with a mismatched dye lot, versus buying too much and wasting money. For a straight layout it comfortably covers edge cuts and a few breakages.
- Do I add waste before or after working out boxes?
- Add waste to the tile count first, then divide by the tiles per box and round up. Rounding up to full boxes usually adds a little more cushion on top of the waste percentage.
- Should I keep leftover tiles?
- Yes. Store spares somewhere dry so you can make an exact match if a tile chips or cracks later. Production lots change often, so the same product bought later may look slightly different.
Our tile calculator applies the right waste factor for your layout automatically, or you can enter a custom percentage. Not sure of your base count yet? Start with how many tiles do I need.
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