Stair calculator

Calculate rise, run, and verify code compliance in seconds

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The Stair Calculator helps architects, builders, and designers quickly determine optimal stair dimensions while ensuring compliance with International Building Code (IBC) requirements.

Simply enter your floor-to-floor height and let the calculator determine the ideal number of risers, tread depth, and total run. The tool automatically checks against IBC limits for residential and commercial applications, flagging any potential code violations before they become costly construction issues.

Whether you're designing a grand staircase for a commercial lobby or fitting stairs into a tight residential renovation, this calculator takes the guesswork out of stair design and helps you deliver code-compliant results every time.

Features

Everything you need

Automatic IBC code compliance checking
Live 2D and 3D stair visualization
Rise and run optimization
Headroom clearance verification
Nosing and tread depth calculations
Support for both residential and commercial codes
Imperial and metric unit support

How it works

Simple workflow

1
Enter the total floor-to-floor height you need to span
2
Specify your preferred riser height or let the calculator optimize
3
Review the calculated dimensions and 2D/3D preview
4
Check the code compliance indicators for any violations
5
Adjust parameters to balance comfort, safety, and space constraints

Use cases

Built for real-world scenarios

Residential renovation

Calculate replacement stairs that meet code requirements while fitting existing floor openings and headroom constraints.

Commercial design

Verify egress stair compliance for office buildings, retail spaces, and multi-family residential projects.

Deck and exterior stairs

Design outdoor stairs with proper drainage slope while maintaining comfortable rise/run ratios.

Code review preparation

Generate accurate stair calculations to include in permit submissions and code review packages.

FAQ

Frequently asked questions

The IBC recommends a maximum riser height of 7 inches (178mm) and minimum tread depth of 11 inches (279mm) for most commercial applications. Residential codes often allow up to 7.75 inches rise. The ideal ratio balances safety with comfort—a 7" rise with 11" run is widely considered optimal.

Divide your total floor-to-floor height by your desired riser height. For example, a 9-foot (108 inch) height with 7-inch risers requires approximately 15-16 risers. The calculator handles this automatically and adjusts for code compliance.

The 18-inch rule states that the sum of one riser plus one tread should equal approximately 17-18 inches for comfortable climbing. This ergonomic guideline helps ensure stairs feel natural to ascend and descend.

The IBC requires a minimum headroom of 6 feet 8 inches (2032mm) measured vertically from the stair nosing to any overhead obstruction. Some residential codes allow 6 feet 6 inches in specific situations.

Have a suggestion?

We're always looking to improve our calculators. If you have ideas for new features, improvements, or found something that could work better, we'd love to hear from you.

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