Stair & Stringer Calculator

Measure the total rise from the landing surface to the top walking surface. The calculator finds the fewest equal risers within your maximum riser height.

Important: This tool is for preliminary material estimation. Structural members, connections, footings, spans and loads must be verified against the applicable code (such as the IRC and your local amendments) and your project requirements.

Tapeline — Stair & Stringer Calculator

Printed September 29, 2026

Total rise36 in
Maximum riser height7.75 in
Tread depth (run per step)10.5 in
Stair width3 ft
Maximum stringer spacing16 in

Results update as you type.

7¾ in is the IRC residential maximum. Some jurisdictions differ.

How it’s calculated

  • Risers = total rise ÷ max riser, rounded up
  • Riser height = total rise ÷ risers
  • Treads = risers − 1 (top step is the deck surface)
  • Stringer = √(rise² + run²)

Worked example

36 in total rise, 7¾ in max riser, 10½ in treads, 3 ft wide.

Inputs

Total rise
36 in
Maximum riser height
7.75 in
Tread depth (run per step)
10.5 in
Stair width
3 ft
Maximum stringer spacing
16 in

Results

Number of risers
5
Riser height
7.2 in
Number of treads
4
Total run
42 in
Stringer length (minimum)
55.32 in
Stringers
4
Stair angle
34.4 °

Load this example into the calculator

Assumptions and limits

  • The top step is the deck or floor surface, so there is one fewer tread than risers.
  • All risers are equal (a code requirement, typically within ⅜ in).

Verify the result against the applicable local code, adopted code edition, manufacturer instructions and project requirements. See our methodology.

Questions

How many steps for a 36 inch rise?

36 ÷ 7.75 = 4.6, so 5 risers of 7.2 in each, with 4 treads.

What are the IRC stair limits?

The IRC sets a maximum riser of 7¾ in and a minimum tread of 10 in for residential stairs. Your jurisdiction may amend these.