Calculator
Tile Calculator
Tile is sold by the box, not the piece, and the box count depends on more than raw floor area — the layout pattern you choose changes how much of every tile ends up in the scrap pile. A straight (grid) lay wastes relatively little; run the same tile diagonally or in a herringbone weave and the waste percentage roughly doubles, because more tiles get cut at odd angles along the edges.
This calculator takes floor area, tile size, and layout pattern to size the order in boxes, with the waste factor baked in per pattern rather than a single flat percentage for every layout. How to measure a room for tile covers the alcove- and jog-heavy rooms this one doesn't handle on its own, and grout and thinset are priced separately in the grout & thinset calculator since they follow a different formula entirely.
Calculate your quantity
10% for straight lay, 15-20% for diagonal or herringbone.
Tile boxes needed
11 boxes
- Area
- 100 sq ft
- Area with waste
- 110 sq ft
- Waste factor
- 10 %
Shopping summary
- • 11 box(es) of tile (10 sq ft/box)
This is an estimate — confirm structural work with a professional.
How this calculation works
Base tile count = floor area / area per tile. Waste percentage is added on top: straight lay runs about 10% (mostly edge cuts and breakage allowance), diagonal lay runs 15% (every cut along a wall is now an angled cut instead of a straight one, and angled cuts break more often), and herringbone or other interlocking patterns run 20% or more because most tiles touching a wall or corner require a custom cut.
Grout line width has a smaller but real effect: a wider grout joint (3/8 inch vs 1/16 inch) slightly reduces how many whole tiles fit per square foot, which this calculator also accounts for in the base count.
The formula
boxes = ceil( length × width × (1 + wastePct/100) / boxCoverage )
- length × width
- Raw floor area in square feet, taken directly from the room dimensions — this formula has no grout-joint or tile-size adjustment built in; joint width's effect on tile count is handled entirely by the separate grout & thinset calculator.
- wastePct
- A single percentage applied to the whole area at once, not a per-cut allowance — the calculator does not know your layout pattern, so the waste field is where a straight, diagonal, or herringbone lay is expressed as a number.
- boxCoverage
- Square feet one box covers, printed on the box — this is an input rather than a constant because box coverage varies by tile size and thickness even within the same product line, and a box sized for 12x12 tile does not hold the same square footage as one sized for 18x18.
Where these numbers come from
- boxes rounded up from area, not from tile count
- The function's own arithmetic never counts individual tiles, only square footage against a box's printed coverage. Retailers sell tile by the box, not the piece, so this matches how the order is actually placed at the counter.
- 10% straight-lay / 15% diagonal / 20%+ herringbone waste
- Trade convention, not a figure this calculator enforces — the waste field defaults to 10% but accepts any value, so the pattern-specific percentage has to be entered deliberately rather than selected from a pattern dropdown.
- no grout-joint deduction in the tile count
- Trade convention: a wider grout joint slightly reduces how many whole tiles physically fit in a given area, but this calculator does not model that effect — it is folded into the base tile-count formula on the grout & thinset calculator instead, which is the more precise place for a joint-width-driven adjustment.
Worked examples
A 9 by 11 foot kitchen floor, straight lay
| Room length | 9 ft |
|---|---|
| Room width | 11 ft |
| Coverage per box | 10 sq ft |
| Waste factor | 10 % |
| Tile boxes needed | 11 boxes |
|---|---|
| Area | 99 sq ft |
| Area with waste | 108.9 sq ft |
| Waste factor | 10 % |
99 sq ft of floor plus 10% waste is 108.9 sq ft, and at 10 sq ft per box that rounds up to 11 boxes — almost a full extra box of headroom over the 10.89 boxes the exact figure implies, purely from the retail rounding rule.
That headroom matters on a kitchen floor specifically: appliance cutouts, an island, and cabinet toe-kicks all generate small cuts a bathroom-style straight run doesn't, so the extra fraction of a box this rounding leaves is a genuine cushion, not pure waste.
The same kitchen, laid on the diagonal
| Room length | 9 ft |
|---|---|
| Room width | 11 ft |
| Coverage per box | 10 sq ft |
| Waste factor | 18 % |
| Tile boxes needed | 12 boxes |
|---|---|
| Area | 99 sq ft |
| Area with waste | 116.82 sq ft |
| Waste factor | 18 % |
Same 99 sq ft floor, an 18% waste figure appropriate to a diagonal lay against square walls pushes the order to 116.82 sq ft — one more box than the straight lay, 12 instead of 11, entirely from the layout decision rather than any change to the room.
The gap between these two orders would widen further on a smaller room: a diagonal cut wastes a roughly constant percentage of the tile touching every wall, so a small kitchen loses proportionally more to that border than a large open floor would.
Common mistakes
- Using a flat 10% waste factor regardless of pattern — diagonal and herringbone layouts genuinely need more, not as a safety margin but because the cutting geometry demands it.
- Buying tile from different production lots — always check the lot/batch number, since shade variation between lots ('dye lot') can be visible once installed.
- Not buying a few extra boxes beyond the waste allowance for future repairs; tile patterns and glazes get discontinued, and matching a cracked tile five years later is often impossible.
- Ignoring that large-format tile (24x24 inches or bigger) needs a flatter subfloor and has less forgiveness for waste-percentage errors, since a miscut large tile is expensive to replace.
- Not dry-laying a test row before committing adhesive, which is the easiest way to catch a layout or centering problem before it's set permanently.
- Rounding the box count down when the calculated need lands just under a full box's coverage, rather than rounding up — a box typically covers a fixed number of whole tiles, and 'almost enough' still means a mid-job store run.
Shopping summary
Order in whole boxes, rounded up from base area plus the pattern-specific waste percentage, all from the same production lot, plus one extra box held back unopened for future repairs — see why you always need 10% extra tile for the fuller case.
Worked example: a 100 sq ft bathroom floor using 12x12 inch tile (1 sq ft each) in a straight lay needs a base count of 100 tiles, plus 10% waste = 110 tiles. If tile is boxed 10 per box, that's 11 boxes. The same room laid on the diagonal needs 100 x 1.15 = 115 tiles, rounding to 12 boxes — one full extra box purely from the layout choice on an identical floor area.
FAQ
Why does herringbone need so much more tile?
Herringbone tiles meet walls and corners at a consistent diagonal angle across the whole field, so almost every border tile requires an angled cut rather than a straight one, and angled cuts have a meaningfully higher breakage rate than square cuts.
Is 10% waste enough for a simple grid layout?
For a rectangular room with a straight lay, yes — 10% comfortably covers edge cuts and normal breakage; irregular rooms with lots of jogs, alcoves, or fixtures (like a bathroom) often run closer to 12-15% even in a straight lay.
Does tile size affect waste percentage independent of pattern?
Somewhat — very large tiles have fewer total cuts but each miscut is more expensive and wastes more material per mistake, while small mosaic tile has many more individual pieces but the sheets themselves are more forgiving of an odd room edge, so the practical waste allowance doesn't move dramatically with size alone the way it does with pattern.
Should grout line width change how many tiles I order?
A wider grout joint slightly reduces the number of whole tiles that fit per square foot compared to a hairline joint, which this calculator's base tile count already accounts for — the effect is usually modest (a few percent) compared to the pattern-driven waste percentage, but it's real on a large floor.
Where to go next
The projects this number is a step of, the guides that explain the method behind it, and the rest of its trade group.