Stair Calculator

Design building stairs complying with building codes (IBC/IRC): calculate total risers, actual riser height, tread depth, and stringer length.

How to use this calculator

1. Enter total vertical rise.
2. Enter target riser height.
3. Read risers, run, and stringer length.

Formula & method

Stair Geometry

Risers = Rise / Target Riser · Stringer = √(Rise² + Run²)

IRC building code model.

Example

120 inch rise → 16 risers @ 7.5 inch, 192.1 inch stringer.

Key insights

• Max riser 7.75", min tread 10" (IRC).

How to interpret your result

Stringer Length

Diagonal support board length.

Frequently asked questions

Rule of thumb?

2R + T = 24 to 25 inches.

Related calculators

• Square Footage Calculator — Calculate area in square feet or square meters for rooms and lots.
• Roofing Calculator — Estimate roofing squares, shingle bundles, and underlayment rolls.

See all other calculators · Explore all online calculators