Carpet quantity: roll width, strip direction and purchased length.
Why can equal room areas require different lengths of carpet from the same roll?
A square-metre price can hide a different order
Both layouts in the example cover the same 12 m² room. The first purchases 16 m² of roll area before allowance; the second purchases 12 m². That difference follows full-width strip cuts, not a change in measured room area.
Include the specified cut extension
If the first layout has a supplied 0.1 m total extra length per strip, each strip is 4.1 m and two strips require 8.2 m. With an illustrative 5% length allowance, the order is 8.61 m. If a selected repeat also applies, align the cut length to that repeat before summing strips.
Use separate room rows
Different rooms can need different strip directions or cut lengths. Enter their supplied layouts separately in the Carpet Calculator. The model sums room strips; it does not promise that leftover width from one room can supply another or that a pattern will match across a proposed seam.
Confirm the quoted purchase unit
A supplier may quote by linear metre of a named roll width or by the resulting purchased square metres. At an illustrative 20 per linear metre, 8.61 m costs 172.20. At 10 per purchased m² on the same 2 m roll, the numerical total is also 172.20. Use the actual roll width and billing basis, not room area.
Use the matching calculator
Use this decision sequence
- Record the selected roll width.
- Identify the strip direction from the supplied room layout.
- Count full-width strips and their specified cut lengths.
- Apply the entered allowance to the resulting length.
Keep the quantities distinct
| Quantity or assumption | How to use it |
|---|---|
| Room area | The measured footprint. |
| Roll length | Sum of full-width cut-strip lengths. |
| Purchased roll area | Purchased length multiplied by roll width. |
Worked comparison
A 4 m × 3 m room and an illustrative 2 m wide roll need two 4 m strips if strips run along the 4 m direction: 8 m roll length before trim. Along the 3 m direction, two 3 m strips need 6 m before trim. The layout choice is supplied, not recommended here.
Check before using the estimate
The tool does not optimise cross-room offcut reuse or choose acceptable seams.
All dimensions, product properties, prices and specifications in this example are illustrative arithmetic inputs. Use the values from your measured plan, selected product data sheet and supplier quote. This guide does not choose construction specifications or certify safety.
Calculation and scope checked 2026-10-13. Methods and scope.