What is the maximum stair riser height?

7 3/4 inches under IRC R311.7 for one- and two-family dwellings, and 7 inches under IBC 1011 for most other occupancies.

What is the minimum tread depth?

10 inches under the IRC and 11 inches under the IBC. A nosing of 3/4 to 1 1/4 inches is required when the tread is less than 11 inches deep.

How many risers do I need for a 9 foot floor-to-floor height?

108 inches divided by a 7 1/2 inch target gives 14 risers at 7 23/32 inches each, with 13 treads. At a 10 inch tread that is a 10 ft 10 in. total run.

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Stair Layout Calculator

Calculate stair geometry including number of risers, riser height, tread depth, total run, and stringer length. Reference: IBC 1011.5 / IRC R311.7

Governing Code

Limits and citations below follow the selected code

Total Rise (inches)

Floor-to-floor height (e.g., 108" = 9 ft)

Target Riser Height (inches)

Typically 7-7.75" (max residential)

Tread Depth (inches)

Minimum 10" residential

Stair Width (inches)

Minimum 36" residential

Nosing Projection (inches)

Typically 0.75"-1.25"; not required when the tread is 11" or deeper

Headroom (inches)

Measured vertically from the nosing line. Minimum 80" (6'-8")

Results

Number of Risers

Actual Riser Height

7 11/16"

7.714"

Number of Treads

Total Run

10'-10"

130.00"

Stringer Length

14'-1"

169.01"

Code Compliance

✓Riser ≤ 7.75"7 11/16" actual · IRC R311.7

✓Tread ≥ 10"10" actual · IRC R311.7

✓Width ≥ 36"36" actual · IRC R311.7

✓Headroom ≥ 80" (6'-8")6'-8" actual · IRC R311.7

✓Nosing 3/4"–1 1/4" (required)1" projection · IRC R311.7

✓Rise between landings ≤ 12'-7"9'-0" total rise · IRC R311.7

2R + T Comfort Rule (should be 24"-25")

2 × 7.71" + 10` = 25.43` - Not in ideal range

Code Reference

IBC 1011.5 / IRC R311.7 – Stair Design. All stairs must comply with riser height, tread depth, and width requirements.

Disclaimer: This calculator is for reference only. Always verify with your local building department.