Stair Calculator

Calculate stair dimensions including rise, run, number of steps, stringer length, and stair angle. Check building code compliance for residential stairs.

Stair Dimensions

Rise

7.20"

per step

Run

10.29"

tread depth

Number of Risers15
Number of Treads14
Stair Angle36.9°
Stringer Length180.00"
Meets Building Code

Units

Measurements

Floor to floor height

Horizontal space available

Including subfloor and finish

Stair Diagram

Total Rise: 108"Total Run: 144.0"Rise: 7.20"Run: 10.29"

Building Code Compliance (IRC 2021)

All measurements meet residential building code requirements

Rise Requirements

Min: 4"

Max: 7.75"

Run Requirements

Min: 10"

Max: 14"

Comfort Analysis

97%

Based on the 2R + T = 25" comfort rule. Your stairs: 2×7.20 + 10.29 = 24.69"

Materials Estimate

14

Treads

15

Risers

2-3

Stringers

180.0"

Stringer Length

Frequently Asked Questions

The ideal residential stair has a rise of 7" (178mm) and run of 11" (280mm). Building codes typically require rise between 4-7.75" and run between 10-14". A comfortable stair follows the rule: 2×Rise + Run = 24-25" (610-635mm).
Divide total rise (floor to floor height) by ideal rise (7"). Round to nearest whole number. For example, 108" total rise ÷ 7" = 15.4, so use 15 risers with 7.2" each.
A stringer is the diagonal structural member that supports the stairs. It's cut with notches for treads (horizontal) and risers (vertical). You typically need two stringers (one on each side), plus a center stringer for stairs wider than 36".
IRC 2021 requires: Rise 4-7.75", Run minimum 10", Width minimum 36", Headroom minimum 80", Handrails on one side minimum. All risers and treads must be uniform within 3/8" variation.
Headroom is the vertical distance from the stair tread nosing to the ceiling above. Building codes require minimum 6'8" (80") headroom at all points. Measure from the nose of each tread to the ceiling directly above.