How this calculator works
Each repeated step contributes a rise and effective tread run to the carpet route. Square-wrap mode adds twice the nosing projection per step. Rounded mode adds that projection allowance plus the difference between a semicircular front and its diameter. This is a simplified profile allowance: avoid counting a nose twice if your measured tread route already includes it. Add landing depth and total fitting allowances, then multiply strip length by strip width.
Formula
strip length = steps x (rise + run + nose allowance) + landing + extra length; square nose allowance = 2 x projection; rounded correction = (pi - 2) x diameter/2; area = length x (stair width + extra width).
Worked example
Ten 0.2 m risers and 0.3 m treads plus a 1 m landing need 6 m before fitting allowance. At 1 m width this is 6 m2, costing $60 at $10/m2.
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Frequently asked questions
Does a waterfall installation need the same wrap?
No. Waterfall and fully wrapped profiles follow different routes. Use no extra wrap when your measured route bridges the nose, or measure the actual path with a flexible tape.
How many steps should I count?
Count the tread-and-riser pairs covered by the strip. Add or remove any separate final riser or landing section in your measurement.
Does this plan seams and roll width?
No. Confirm carpet pile direction, roll width, joins and fitting allowances with the installer.