Accessories

Stair runner length calculator with underlay

Underlay on stairs does two jobs: it makes the runner feel right underfoot, and it takes the abrasion off the nosings where wear concentrates. Skipping it roughly halves a runner's life.

You can buy it as continuous underlay cut to the runner length, or as pre-cut pads — one per tread.

Your staircase

Start from typical stair sizes where you live

IRC-style stairs: 10 in minimum tread, 7¾ in maximum riser. Runners are usually 27 in or 32 in wide and sold by the linear foot.

Number of stairs

Count every step you will cover.

Tread depth (in)

Front edge to back of the step. Fractions like 10 1/2 work.

Riser height (in)

The vertical face between two treads.

Waste allowance

Custom%

10% is a common starting point; pattern matching and winders need more.

Add a nosing / overhang allowance per step

Needed when the runner wraps around a projecting nose (Hollywood installs and thick pads). Waterfall installs usually don't need it.

Your stair runner length

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

Recommended purchase length

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.

Your measurements, drawn to scale

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.

Continuous underlay

Priced by the same linear unit as the runner and cut to the same length. Simple to order, slightly more material, and it runs down the risers as well as over the treads.

Cut pads per tread

One pad per tread, sized to sit slightly narrower than the runner and to wrap over the nosing. The calculator counts one pad per tread automatically, so a 15 step flight shows 15 pads.

Thickness and grade

A denser, thinner underlay performs better on stairs than a thick soft one, which can let the runner move underfoot. Use the underlay price field to compare two grades on total cost.

Questions people ask

Do I need underlay under a stair runner?: Yes on almost every job. It protects the nosings, improves comfort and significantly extends the life of the runner.
How many stair pads do I need?: One per tread. A 15 step flight needs 15 pads; landings take a separate cut piece.

Related guides

See all stair runner calculator guides