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Stair Stringer Calculator · Free calculator

Stair Stringer Calculator: 24" Total Rise

For 24" from finished floor to finished floor (2' 0"), you need 4 risers of 6" and 3 treads. With 10" treads the stairs run 2' 6" and each stringer is 3' 2-7/16" long — cut from a 8' 2x12.

Quick answer

Risers
4 × 6"
Treads (10")
3
Total run
2' 6"
Stringer length
3' 2-7/16"
2x12 stringers (36" wide)
3 × 8'
IRC
✓ Meets code

▍Stair Stringer Calculator

in
Tread depth (run)
in
Risers × height
4 × 6"
✓ Meets IRC (riser ≤ 7-3/4", tread ≥ 10")
2' 0"RUN 2' 6"
Treads
3
Total run
2' 6"
Stringer length
3' 2-7/16"
Angle
31.0°
2x12 stringers
3 × 8'
2R + T
22.00in

24" rise — tread depth options

TreadTotal runStringerAngle2R + TStock
10"2' 6"3' 2-7/16"31.0°22.008'
10-1/2"2' 7-1/2"3' 3-5/8"29.7°22.508'
11"2' 9"3' 4-13/16"28.6°23.008'
1' 0"3' 0"3' 7-1/4"26.6°24.008'

24" 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
38"2No — too tall
46"3Yes
54-13/16"4Yes
64"5Yes

How the math works

  1. Risers = 24" ÷ 7.75" max = 3.10 → round up to 4
  2. Riser height = 24" ÷ 4 = 6.0000" ≈ 6"
  3. Treads = risers − 1 = 3
  4. Total run = 3 × 10" = 2' 6"
  5. Stringer = √(24² + 30.0²) = 3' 2-7/16"

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 24" 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 24 inch rise?

4 risers (steps up) of 6" each, with 3 treads. That stays under the IRC maximum riser height of 7-3/4".

How long of a stringer do I need for a 24" rise?

3' 2-7/16" along the slope with 10" treads (total run 2' 6"). Buy 8' 2x12s to leave room for the top and bottom cuts.

What is the riser height for a 24" stair?

6.000" — about 6" on the tape. 2R + T = 22.00", outside the 24"–25" comfort range — consider adjusting tread depth.

What angle are 24" stairs?

31.0° with 10" treads. Residential stairs typically fall between 30° and 37°.