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Stair Stringer Calculator · Free calculator

Stair Stringer Calculator: 108" Total Rise

For 108" from finished floor to finished floor (9' 0"), you need 14 risers of 7-11/16" and 13 treads. With 10" treads the stairs run 10' 10" and each stringer is 14' 1" long — cut from a 16' 2x12.

Quick answer

Risers
14 × 7-11/16"
Treads (10")
13
Total run
10' 10"
Stringer length
14' 1"
2x12 stringers (36" wide)
3 × 16'
IRC
✓ Meets code

▍Stair Stringer Calculator

in
Tread depth (run)
in
Risers × height
14 × 7-11/16"
✓ Meets IRC (riser ≤ 7-3/4", tread ≥ 10")
9' 0"RUN 10' 10"
Treads
13
Total run
10' 10"
Stringer length
14' 1"
Angle
37.6°
2x12 stringers
3 × 16'
2R + T
25.43in

108" rise — tread depth options

TreadTotal runStringerAngle2R + TStock
10"10' 10"14' 1"37.6°25.4316'
10-1/2"11' 4-1/2"14' 6-1/16"36.3°25.9316'
11"11' 11"14' 11-3/16"35.0°26.4316'
1' 0"13' 0"15' 9-3/4"32.7°27.4318'

108" 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
138-5/16"12No — too tall
147-11/16"13Yes
157-3/16"14Yes
166-3/4"15Yes

How the math works

  1. Risers = 108" ÷ 7.75" max = 13.94 → round up to 14
  2. Riser height = 108" ÷ 14 = 7.7143" ≈ 7-11/16"
  3. Treads = risers − 1 = 13
  4. Total run = 13 × 10" = 10' 10"
  5. Stringer = √(108² + 130.0²) = 14' 1"

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 108" 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 108 inch rise?

14 risers (steps up) of 7-11/16" each, with 13 treads. That stays under the IRC maximum riser height of 7-3/4".

How long of a stringer do I need for a 108" rise?

14' 1" along the slope with 10" treads (total run 10' 10"). Buy 16' 2x12s to leave room for the top and bottom cuts.

What is the riser height for a 108" stair?

7.714" — about 7-11/16" on the tape. 2R + T = 25.43", right in the comfortable range.

What angle are 108" stairs?

37.6° with 10" treads. Residential stairs typically fall between 30° and 37°.