About The Stair Calculator
A free, browser-based stair calculator that turns one measurement into clear numbers and a diagram you can build from.
Why we built it
Stair math trips up beginners and experienced builders alike. One wrong number — a mismeasured rise, a forgotten tread thickness — can ruin a set of stringers or leave you with stairs that fail inspection. We built The Stair Calculator to make that math fast, clear, and reliable for DIYers, carpenters, contractors, and inspectors.
The calculator is completely free. There is no account, no sign-up, and nothing to install.
What the calculator does
Enter your total rise and a target riser height (or a fixed number of risers), then either a tread going or the total run you have available. Add tread thickness, nosing, and the top tread position under Construction details, and work in inches, feet, millimeters, centimeters, or meters. The tool instantly returns:
Steps
The number of risers, the exact riser height, and the number of treads on each stringer.
Space
The total run, so you know exactly how much floor space the stairs will take.
Stringers
Stringer pitch length, the first stringer rise cut, the top support position below the upper floor, and layout points for every tread.
Checks & diagram
The stair angle, a 2021 IRC reference check, a 2R + G comfort comparison, and a live diagram you can print, save as a PDF, download as an SVG, or export to CSV.
Landings
A two-flight landing planner that splits the rise between flights with one equal riser height and shows the landing height and footprint.
Accuracy, assumptions, and code notes
- Equal risers: the total rise is always divided into identical risers, and the count is rounded up so no riser is taller than your target.
- Code checks: results are compared with widely adopted International Residential Code (IRC) limits, such as a 7¾" maximum riser, a 10" minimum tread, the nosing range, and the 151" maximum rise for one flight.
- Stringer pitch length: the tread count multiplied by the length of one rise-and-go step. It is not the board length to order — allow extra for end cuts, bearing, and connections.
- Local code always wins. Requirements vary by jurisdiction. Use the results as a planning aid, confirm them with your building department, and measure the actual structure before cutting.
Accessibility and privacy
- Accessible: labeled inputs, full keyboard support, and results announced to screen readers.
- Private: every calculation runs in your browser. Your measurements are never sent to or stored on our servers. Read our privacy policy for details.
- Fast: the site is lightweight and works on phones, tablets, and job-site laptops.
Who we are
Adam
A general contractor with more than 15 years of hands-on experience in residential framing and deck building. After seeing countless projects stall on stair math, Adam launched The Stair Calculator to help DIYers and fellow pros get it right the first time. He writes our construction, code, and calculation guides.
Liam
Liam writes our guides on stair safety, tools, deck stairs, and reading stair diagrams, turning trade know-how into clear, practical steps.
Get in touch
Found a bug, have a feature idea, or want to embed the calculator on your site? We’d love to hear from you at [email protected] or through our contact page.