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Calculation Machine

Stair Stringer Calculator

Rise, run and stringer length for stairs.

Reviewed by James Whitfield · How we check our maths

Your values

ⓘ Live results

Results
Number of steps
14
Actual riser height
7.71 in
Actual tread depth
9.43 in
Stringer length
14.21 ft (170.6 in)
Stair angle
39.3°

Quick answer

The calculator divides total rise by a target riser height to find the number of steps, then sizes the stringer.

The formula

steps = round(total rise / target riser); stringer length = sqrt(rise^2 + run^2)

Worked example

Worked example

Using the values the calculator loads with.

Inputs

  • Total rise108 in
  • Total run132 in
  • Target riser height7.5 in

Result

  • Number of steps14
  • Actual riser height7.71 in
  • Actual tread depth9.43 in
  • Stringer length14.21 ft (170.6 in)
  • Stair angle39.3°

How to use the Stair Stringer Calculator

  1. 1Measure the total rise from finished floor to finished floor.
  2. 2Measure or plan the total horizontal run available.
  3. 3Set a target riser height (code max is usually 7.75 in) and get exact steps and stringer length.

Frequently asked questions

What riser height is code?

Most residential codes cap risers at 7.75 in with a minimum tread of 10 in, but always check local code.

Why round the number of steps?

You need a whole number of equal steps; the calculator adjusts riser height slightly to keep them even.

About this calculator