How to use the stair runner length calculator
- Enter the number of steps the runner will cover, the rise of one step and the run of one tread in inches.
- Choose whether the runner covers riser and tread, or treads only.
- Add any landing length, and an allowance for ends and trimming.
- Read the length of runner to buy in feet. Add a price per foot for a cost estimate.
Formula
Length per step = rise + run (riser and tread), or run (treads only)
Length to cover = steps x length per step + landing
Total length = length to cover + extra for ends and trimming
Feet to buy = total length / 12, rounded up to a whole foot
Measure the run to include the nosing if the runner wraps over it.
13 steps with a 7.5 inch rise and 10 inch run
Each step uses 7.5 + 10 = 17.5 inches. Thirteen steps cover 227.5 inches. With a 12 inch allowance for ends the total is 239.5 inches, or 19 feet 11.5 inches, so you buy 20 feet of runner.
If the runner covers treads only, 13 steps need 130 inches, so 11 feet with no allowance. Adding a 36 inch landing to the full runner and no allowance gives 263.5 inches, so 22 feet, and at $12 a foot that is $264.
Waterfall and tread-only runners
A runner that flows over the nosing and down the riser to the next tread is often called a waterfall style, and it uses the rise plus the run of every step. A runner that lies on the treads with bare risers between needs only the run of each tread.
Choose the option that matches how yours will be installed. If your runner turns a corner or goes over a winder, the real length will differ from this straight calculation.
Measuring and buying
Measure rise and run on a few steps, since old stairs are rarely perfectly even. Add the spare allowance to cover the end folds, mistakes and trimming at the top and bottom. Many runners are cut to length from a roll, but some come in fixed lengths, so ask the supplier how yours is sold.
Padding, patterns that must match and stair noses with a different profile are not modeled. For floor covering by area use the carpet calculator, for the stairs themselves see the stair stringer calculator, for sizing a rug try the rug size calculator, and for area use the square footage calculator.
Assumptions and limits
- Every step has the same rise and run, in inches.
- The runner follows a straight flight with no turns or winders.
- The landing and the extra allowance are lengths you enter.
- Padding thickness and pattern matching are not included.
Frequently asked questions
How do you calculate stair runner length?
Add the rise and run of one step, multiply by the number of steps, add any landing and a spare allowance, and divide by 12 for feet. Thirteen steps of 7.5 and 10 inches is 227.5 inches before the spare.
How much extra runner should I buy?
The tool has a box for extra length with 12 inches as an example. Folds, trimming and mistakes decide how much you want, so adjust it.
Does the runner go over the risers?
That is your choice. A waterfall style covers the riser and tread, while a tread-only runner covers just the treads.
Why does the tool round up to whole feet?
Runners are usually sold by the foot or cut to a whole length, so rounding up avoids coming up short.