Carpet Calculator
Compare two straight-strip layouts for a rectangular room. See how fixed roll width changes the length you purchase, even when the room’s floor area stays the same.
Changing a unit selector reinterprets the numbers; it does not convert your entries. Update the inputs before calculating. Prices are examples in your own currency.
Why carpet area is different from room area
Carpet is bought from a roll with a fixed width. A 5 × 3.6 m room has 18 m² of floor, but a 4 m-wide roll cannot be purchased as exactly that shape. This tool compares parallel strips in each orientation. It does not reuse offcuts, mix pile directions or optimise a whole-house cutting plan.
Worked example
For a 5 × 3.6 m room, a 4 m usable roll and 0.05 m trimming on each edge, layout A uses one strip 5.1 m long: 20.4 m² purchased. Layout B needs two strips, each 3.7 m long: 29.6 m² purchased. With plain carpet, 0.1 m cut increments and a price of 20/m², the costs are 408 and 592.
How do pattern repeat and trimming work?
The tool adds the edge allowance twice to each room dimension. It rounds each strip length up to a full longitudinal pattern repeat, if entered, then up to the supplier’s cut increment. This is a conservative allowance model. It does not match a transverse repeat or account for seam trimming; a patterned installation requires a fitter’s cut plan.
Can I rotate the carpet to use less?
The comparison shows both mathematical layouts, but the cheaper one is not automatically suitable. Pile direction, light, adjoining rooms and seam locations can decide the acceptable orientation. Enter usable width after any supplier or fitter deductions; nominal roll width and tolerances may differ. Do not rotate individual strips within one installation.
How should I measure an irregular room?
Measure at the widest points and include recesses and doorways, or ask your fitter for a plan. This calculator models one rectangle only. The difference between purchased and room area includes trim and offcuts; it is not all recoverable waste. Underlay, grippers, fitting and stairs are excluded.
Measuring reference: Online Carpets room and roll-width guide.
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Reviewed 5 November 2026. Free, no signup. Calculations run in your browser. Confirm measurements and product specifications before ordering. Costs exclude labour, tax and delivery.