Spike's Calculators


Stringer Length Calculator

Calculate the length of a stringer from the total rise, the number of risers and known run of one tread.

The number of Risers

To see the number of risers, divide the total rise by a riser height that works for you. For instance, convert this to a decimal if you like a 7 1/2" riser. 7 1/2" = 7 + 1 ÷ 2 = 7.5 inches.

Do the same for the total rise, converting it to decimal. Close counts. It can be less than 100% accurate. The total rise = 8'- 2 1/4", then multiplying the 8 x 12 = 96 inches and adding 2 for a total rise of 98 inches. Then 98 ÷ 7.5 = 13 (rounded). Entering 13 for the number of risers is a good start.

Stringer Length Calculator

Length of a Stair Stringer Calculator

Total Rise ft in n
Number of Risers#
Run in n


Total Rise in Inches in
Height of Riser in
Total Run ft in
Stringer Length ft in

The Calculation

  1. enter total rise in feet inches and fraction of an inch
  2. enter the number of risers you wish to calculate for
  3. enter the run (depth of one tread, minus the nosing), in inches and fraction of an inch

The Results

  1. total rise converted to inches
  2. the height of one riser
  3. total run of stairs
  4. the length of the stringer

Note: after you enter the total rise and the run measurements try different values for number of risers till you get a riser result that you are happy with. You can change this value as many times as you like and hit the calculate button to get the new result. If you hit the reset button, it will clear all values and you will have to start all over again.

The height from top of floor to top of next floor has a total rise of 9 feet 1 and ½ inches
the number of risers you are calculating for is 14
the depth of one tread (run) minus the nosing is 9 and ⅝ inches

Spike's Calculators

The Results

the total height of 9' 1 ½" converted to inches is 109 ½ inches
the height (rise) of each tread is 7 13/16 inches
the total run of the stairs is 10 feet 5 and ¼ inches
the length of the stringer is 13 feet 5 and ¼ inches
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