Waste factor reference table
How much extra material to order, by what you are laying and how you are laying it — and why the usual flat 10% is wrong more often than it is right.
The short version
Waste is not caused by the room. It is caused by cuts. Every piece of material that meets a wall, a door frame, a corner or a pipe gets cut, and most offcuts cannot be used anywhere else. A layout that forces more cuts per square metre wastes more material, and the amount is predictable enough to put in a table.
The allowance used across this site is built from three separate additions, not one number:
total waste = pattern waste + room-shape addition + small-room addition
They add rather than multiply, because they describe independent causes. A herringbone floor in a complicated small bathroom really does need about 18 + 5 + 4 = 27% extra, and anyone who has run short 80% of the way through one will tell you that figure is not padded.
Tile patterns
| Pattern | Waste | Why |
|---|---|---|
| Straight / stack bond | 10% | Cuts occur only at the perimeter, and an offcut from one edge often serves the opposite edge. |
| Brick bond, 50% offset | 11% | Alternate rows start with a half tile, which is a cut — but the other half is usually usable. |
| Brick bond, 1/3 offset | 12% | Three-row repeat means two of every three row-starts are cuts, and the remainders match less often. |
| Diagonal 45° | 15% | Every perimeter tile becomes a triangle. Two triangles rarely make one usable tile because the cut runs the wrong way. |
| Basketweave | 15% | The module has to land whole; anything that does not fit the module at the edge is scrap. |
| Modular / multi-size | 15% | You must buy sizes in the ratio the pattern needs, not the ratio the room needs, so some sizes are left over. |
| Herringbone | 18% | The perimeter is an unbroken run of compound cuts, and the pattern itself cannot absorb an odd offcut anywhere. |
Plank flooring layouts
| Layout | Waste | Why |
|---|---|---|
| Straight, along the long wall | 8% | The offcut from the end of each row starts the next row, which is also how you get the required stagger. Very little is scrapped. |
| Straight, across the room | 10% | More rows, more end cuts, and the offcuts are shorter so fewer of them are long enough to reuse. |
| Diagonal 45° | 15% | Both ends of every plank are angle cuts against the wall. |
| Herringbone / chevron | 20% | Planks are pre-cut to a fixed module and the perimeter is all compound cuts. Chevron planks are also handed — left and right are not interchangeable. |
Other materials
| Material | Allowance | Notes |
|---|---|---|
| Plasterboard / drywall, simple room | 10% | Offcuts around openings are rarely large enough to use elsewhere. |
| Plasterboard, many openings or a stairwell | 15% | Every opening generates two unusable offcuts. |
| Concrete, poured into formwork | 5% | Formwork is accurate; the loss is spillage and what stays in the barrow. |
| Concrete, poured against excavated earth | 10% | Trench sides slump and the base is never flat. Always measure the trench you dug, not the one you set out. |
| Carpet | 10–15% | Sold in fixed roll widths, so waste is set by how your room divides into that width, not by a percentage. Plan the cuts. |
| Sheet vinyl | 10% | As carpet, plus a pattern-repeat allowance if it has one. |
| Skirting and trim | 10% | Mitres eat length, and a mis-cut mitre costs a whole length rather than a little. |
| Paint | 0% | Paint has no cutting waste. What it has is an absorption penalty on the first coat — a different problem, covered in the coverage rates. |
The room-shape addition
| Room | Add | Description |
|---|---|---|
| Simple | 0% | A rectangle with square corners. One doorway. Nothing in the middle of the floor. |
| Normal | +2% | One or two cut-outs: a WC pedestal, a kitchen island, a chimney breast, a second doorway. |
| Complex | +5% | Several cut-outs, alcoves, a bay, walls that are not square to each other, or anything curved. |
Test for "complex": count the internal corners in the floor outline. A rectangle has none. Each one is a place where two rows of cuts meet and offcuts stop being reusable.
The small-room addition
Waste is usually quoted as a percentage, which quietly assumes the loss scales with the area. It does not. A single ruined cut — a chipped edge, a tile snapped on the wrong side of the line, a plank cut 10 mm short — costs the same one piece whether the room is 3 or 40 square metres. In a small room that one piece is a much bigger share of the order.
| Net area | Add |
|---|---|
| Under 3 m² (32 ft²) — cloakroom, shower enclosure | +6% |
| 3–6 m² (32–65 ft²) — small bathroom | +4% |
| 6–12 m² (65–130 ft²) — bathroom, small bedroom | +2% |
| Over 12 m² (130 ft²) | 0% |
Small rooms also have a higher ratio of perimeter to area, which is the same thing said differently: proportionally more of the floor is made of cut pieces.
Three worked examples
A 12 m² kitchen floor, 600 × 600 porcelain, straight
10% pattern + 2% shape (island and two doorways) + 2% small room = 14%. Order 13.7 m², which at 4 tiles per box rounds to 10 boxes and gives you 14.4 m².
A 4 m² bathroom floor, 300 × 300, diagonal
15% pattern + 5% shape (WC, basin pedestal, awkward corner) + 4% small room = 24%. On 4 m² that is under a square metre of extra tile — roughly the price of a takeaway, against the certainty of a shade mismatch if you run out.
A 28 m² living room, laminate, straight along the long wall
8% pattern + 0% shape + 0% small room = 8%. This is the case where the flat 10% rule over-orders, and on a big floor that is a real amount of money. Ordering by pattern rather than by rule of thumb saves roughly half a pack here.
Why the direction of the error matters. Over-ordering costs you the price of the surplus and gives you repair stock. Under-ordering costs you a second delivery, a likely batch mismatch in shade, and sometimes the whole job re-done. The two errors are not symmetrical, which is why every figure in this table is rounded up rather than down.
When to ignore the table entirely
- Material you cannot re-order. Clearance stock, a discontinued line, reclaimed brick or timber, anything imported one-off. Buy every piece you can afford at the time of the first order.
- Roll goods. Carpet, sheet vinyl, wallpaper. Waste depends on how your room divides into the roll width or the pattern repeat, and can be anywhere from 5% to 40%. A percentage is meaningless here; lay the cuts out on paper.
- Your first time. If you have never cut this material before, add 5%. You will break some learning, and that is a cheaper way to learn than running out.
- Tile with a strong directional pattern or heavy shade variation. You will reject pieces on appearance as well as on fit. Add 5%.
Use it
Every calculator on this site applies these figures automatically once you pick the pattern and room shape:
Last reviewed 2026-09-18. These allowances are our own working figures, assembled from merchant estimating practice and manufacturer fitting guidance, and are deliberately rounded up. They are planning estimates, not a guarantee.