Stair Calculator

Enter your total rise and available run to calculate the number of steps, individual riser height, tread depth, stringer length, and stair angle — with automatic IRC code compliance checks.

Stair Calculator

Total Rise (in)

Total Run Available (in)

Desired Riser Height (in)

Tread Depth (in)

Tread Nose Overhang (in)

Stair Width (in)

Number of Stringers

Stair Profile

Hover for details • side profile (showing 8 of 14 steps)

Number of Risers

13 treads

Actual Riser Height

7.71"

Target was 7.5"

Tread Depth

10"

11" with 1" nosing

Stringer Length

14' 1"

169.0" diagonal

Stair Angle

39.7°

Steep — consider more run

Actual Total Run

10' 10"

130.0" horizontal

Code Check	IRC Requirement	Status
Riser height (7.71")Best value	Max 7.75"	PASS
Tread depth (10")Best value	Min 10"	PASS
Stair width (36")Best value	Min 36"	PASS
Comfort rule (17.7")Best value	17"–18"	PASS
Total run (130.0")	Available: 120"	FAIL

Staircase exceeds available spaceThe calculated total run of 10' 10" exceeds the available horizontal space of 10' 0". Consider increasing the riser height (within code limits) or reducing tread depth to shorten the run.

Stringer lumber: use 2x12 boardsMost residential stairs require 2x12 lumber for stringers. Your stringer length of 14' 1" means you need at least a 15-foot 2x12 board per stringer (3 stringers total). For stairs wider than 36", add a center stringer every 16-18 inches of width.

This design meets IRC code and comfort guidelinesA riser + tread sum of 17.7" falls within the 17-18" comfort range. Stair angle of 39.7° is outside the ideal 30-35° range but still code-compliant.

This calculator provides stair geometry estimates based on IRC residential code guidelines. Always verify with your local building department — codes vary by jurisdiction and commercial stairs have different requirements.