How To Calculate Carpet Wastage
Quick answer
Carpet waste = carpet ordered − room area. Work out what you have to order from the roll (drops × cut length × roll width), take away the room’s area, and divide by what you ordered for the waste percentage. Flat rules of thumb (10–15%) are only a starting point; the roll width decides the real figure.
Definition
Carpet wastage is the carpet you pay for but do not lay: trim at the walls, the unused width beside the last drop, cut-outs for alcoves, and extra to match a pattern or pile direction.
Explanation
Because carpet is sold off rolls of fixed width, the waste on a room can be anything from about 5% to over 30%. A 3.9 m wide room on a 4 m roll wastes very little; a 4.1 m wide room on the same roll needs a second drop and can waste a third of what you buy. That is why calculating the actual cut plan beats adding a flat percentage.
Typical waste on carpet jobs
| Situation | Typical waste |
|---|---|
| Room just under the roll width | 5–10% |
| Room just over the roll width (second drop) | 20–35% |
| Stairs and landings | 15–25% |
| Patterned carpet | Add the pattern repeat per drop |
Examples
- 5.2 m × 4.3 m room (22.36 m²) on a 4 m roll: order 35.2 m², waste 12.84 m² = 36%.
- Same room on a 5 m roll: order 26.5 m², waste 4.14 m² = 16%.
Summary
Work out waste from the roll, not from a percentage. The free carpet roll calculator shows the real waste for any room, and PlanCutFit shows it for every room on the job before you price it.
In depth
Working it out
Where carpet waste comes from
Most waste is the unused width beside the last drop, not trim.
- Trim at the walls (about 10 cm per cut)
- Unused roll width beside the last drop
- Alcoves, bays and chimney breasts
- Pattern repeat and pile direction
- Stairs cut from leftover widths
The calculation
Waste % = (carpet ordered − room area) ÷ carpet ordered × 100. Carpet ordered = drops × (length + trim) × roll width.
Cutting the waste down
Try the other roll width, turn the drops the other way, or plan stairs and small rooms from the leftovers. Doing it per job rather than per room is where the real savings are.
Frequently asked questions
- What waste percentage should I use for carpet?
- Use the cut plan rather than a flat figure. If you must use a rule of thumb, 10% for simple rooms and 15–20% for stairs or awkward shapes, then check the roll width.
- Should waste be on the customer’s quote?
- Yes. The customer pays for what comes off the roll. Show it as the carpet quantity, and explain that roll widths are fixed if they ask.
Related resources
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