Planning carpet pieces for spiral stairs

A spiral stair cannot take a continuous runner — every tread is a wedge, and the runner would twist. What people actually fit is a set of individually cut and bound tread pads.

To estimate material, work out the depth of one tread on the runner's centre line, multiply by the number of treads, then add generous waste for the wedge shape.

Your staircase

Optional starting measurements

Example measurements only, not building-code advice. Replace them with measurements from your own stairs.

Check a few steps before using one set of measurements for the whole flight.

Number of stairs

Count the tread-and-riser pairs the runner will cover. Exclude landings.

Tread depth (in)

Measure the runner path across the flat tread. Fractions like 10 1/2 work.

Riser height (in)

The vertical face between two treads.

Waste allowance

Custom%

10% is the starting allowance here, not a guarantee. Ask your fitter about patterns and turns.

Add a nosing / overhang allowance per step

Enter the extra runner path around the edge, including any underside wrap. Do not add it twice if it is already included in your measurements.

Your runner estimate

20 ft 3.1 in

Total runner required for 13 steps, including a 10% waste allowance.

Total runner length in each unit
Inches	243.1 in
Feet	20.26 ft
Feet & inches	20 ft 3.1 in
Yards	6.75 yd
Meters	6.17 m
Centimeters	617.47 cm

Length to order

21 ft

7 yd · 6.4 m · 252 in

This calculator provides an estimate based on the measurements and installation assumptions you enter. Complex, curved or winder staircases may require professional measurement.

One step, shown in profile

Side elevation of a staircase. The runner travels across each tread and down each riser, so every step consumes tread depth plus riser height of material.

Estimating spiral tread pads

Measure the tread depth at the point where the middle of the pad will sit. Twelve centre-line measurements of 12 in add to 144 in, but that is not enough information to order carpet: the widest cut, wrap, shape and roll width must also be measured.

Risers are usually left bare

On spirals the risers are often open or metal, so no riser allowance is needed. For tread-only pieces, calculate the material from the measured templates separately; do not use the standard tread-plus-riser result as an order quantity.

Binding and fixing

Every pad needs its edges bound, and fixing must follow the carpet maker’s and installer’s instructions for that tread surface. Get binding and fitting priced separately for each piece.

Questions people ask

Can you put a runner on a spiral staircase?: Not as one continuous piece. Spiral stairs take individually cut, bound tread pads shaped to each wedge.
How much material do spiral tread pads use?: Use templates of the finished pieces and a cutting layout for the available roll width. Centre-line depth multiplied by tread count cannot determine the area or cutting waste for wedges.

Related guides

See all stair runner calculator guides