Carpet Calculator — Room Area, Rolls & Waste
Estimate carpet rolls, underlay, and waste for any room size.
Quick answer
Enter room length and width, roll width, and waste percentage. The calculator returns carpet area, linear metres on the roll, and optional underlay and gripper quantities.
Try the calculator
Results
- Net floor area
- 20.8 m²
- Order quantity (with waste)
- 22.88 m²
- 4m roll — strips needed
- 2
- Carpet to purchase (before waste)
- 32 m²
- Seams
- 1
- Underlay (incl. 5% overlap)
- 21.84 m²
- Gripper rod required
- 16.8 m
- 1.5m gripper strips
- 12 strips
- Room perimeter
- 18.4 m
- • Seam positions approx. every 4m across room width.
Definition
A carpet calculator estimates how much carpet, underlay, and accessories you need based on room dimensions, roll width, and fitting waste.
Explanation
Carpet is sold by the square metre or linear metre on fixed roll widths (typically 4m or 5m in the UK). Fitters add waste for joins, pattern matching, and awkward cuts. Gripper rod runs around the perimeter, and door bars bridge transitions at doorways.
Advantages
- Avoids under-ordering on large rooms
- Accounts for roll width and waste in one step
- Helps price jobs accurately before the survey
Disadvantages
- Stairs and landings need a separate stair calculator
- Patterned carpet may need extra waste beyond 10%
Worked example
A 4m × 5.2m lounge (20.8 m²) with 10% waste needs 22.9 m² of carpet. On a 4m roll that is 5.73 linear metres, plus perimeter gripper and one door bar.
Examples
- Measure the room at the longest points
- Choose roll width (usually 4m or 5m)
- Add 10–15% waste for plain carpet, more for patterns
- Add gripper for the full perimeter minus doorways
Summary
Use the carpet calculator to convert room dimensions into order quantities with sensible waste, then verify on site before ordering.
In depth
How professional fitters measure and order carpet
Accurate carpet take-offs protect margin on every job — short orders destroy profit on revisits.
Start with a room sketch
Before you touch a tape measure, draw the room as a rectangle first — even L-shaped spaces are split into blocks on paper. Mark doors, fireplaces, and built-in cupboards because gripper stops at openings, not across them.
Measure at floor level, not skirting top, and always record the maximum length and width even if walls look parallel. Older properties especially can taper by several centimetres over a 4m span.
Plan roll direction before you calculate
UK carpet usually arrives on 4m or 5m rolls. The roll runs along the length of the cut, so a 4m × 5.2m room might need a single 4m-wide piece roughly 5.2m long — but an L-shape or hall-through-lounge can force a join.
Put the join where foot traffic is lowest (behind a sofa, under a bed) and note pattern direction if the carpet is directional or striped.
Build up the full order list
A complete carpet quote rarely stops at the face cloth. Underlay is ordered by floor area, gripper by perimeter minus doorways, and door bars at every transition.
On stairs, switch to the stair carpet calculator — flat-room maths will under-order every time because treads, risers, and bullnoses eat extra material.
Frequently asked questions
- How much waste should I add for carpet?
- Plain carpet: 10%. Patterned or directional pile: 12–15%. Complex rooms with many corners: up to 20%.
- What roll width should I use?
- Use the widest roll that fits the room without a join if possible. Common UK widths are 4m and 5m.
Related resources
Automatic internal links for calculators, guides, glossary, and directory pages.
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