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Stair Stringer Calculator · Free calculator

Stair Stringer Calculator: 36" Total Rise

For 36" from finished floor to finished floor (3' 0"), you need 5 risers of 7-3/16" and 4 treads. With 10" treads the stairs run 3' 4" and each stringer is 4' 5-13/16" long — cut from a 8' 2x12.

Quick answer

Risers
5 × 7-3/16"
Treads (10")
4
Total run
3' 4"
Stringer length
4' 5-13/16"
2x12 stringers (36" wide)
3 × 8'
IRC
✓ Meets code

▍Stair Stringer Calculator

in
Tread depth (run)
in
Risers × height
5 × 7-3/16"
✓ Meets IRC (riser ≤ 7-3/4", tread ≥ 10")
3' 0"RUN 3' 4"
Treads
4
Total run
3' 4"
Stringer length
4' 5-13/16"
Angle
35.8°
2x12 stringers
3 × 8'
2R + T
24.40in

36" rise — tread depth options

TreadTotal runStringerAngle2R + TStock
10"3' 4"4' 5-13/16"35.8°24.408'
10-1/2"3' 6"4' 7-5/16"34.4°24.908'
11"3' 8"4' 8-7/8"33.2°25.408'
1' 0"4' 0"5' 0"31.0°26.408'

36" rise — riser count options

IRC R311.7.5.1: riser height 7-3/4" max. Comfortable stairs land at 7"–7-1/2".

RisersRiser heightTreadsMeets IRC
49"3No — too tall
57-3/16"4Yes
66"5Yes
75-1/8"6Yes

How the math works

  1. Risers = 36" ÷ 7.75" max = 4.65 → round up to 5
  2. Riser height = 36" ÷ 5 = 7.2000" ≈ 7-3/16"
  3. Treads = risers − 1 = 4
  4. Total run = 4 × 10" = 3' 4"
  5. Stringer = √(36² + 40.0²) = 4' 5-13/16"

Subtract one tread thickness from the bottom riser of the stringer (drop the stringer) so the first step matches the rest.

Trade pro tips

  • Measure the 36" rise from finished floor to finished floor — add flooring and tread thickness to rough measurements.
  • Cut one stringer, test it in place, then trace it for the rest.
  • At 36" wide, use 3 stringers; at wider than 36", add one stringer per 16"–18".

Frequently asked questions

How many steps for a 36 inch rise?

5 risers (steps up) of 7-3/16" each, with 4 treads. That stays under the IRC maximum riser height of 7-3/4".

How long of a stringer do I need for a 36" rise?

4' 5-13/16" along the slope with 10" treads (total run 3' 4"). Buy 8' 2x12s to leave room for the top and bottom cuts.

What is the riser height for a 36" stair?

7.200" — about 7-3/16" on the tape. 2R + T = 24.40", right in the comfortable range.

What angle are 36" stairs?

35.8° with 10" treads. Residential stairs typically fall between 30° and 37°.