Stair Calculator

About Stair Calculator

Stair Calculator is a free online tool for builders, contractors and DIY homeowners who need to lay out a staircase quickly and accurately. Enter a total rise and a target step height, and it works out the number of steps, the exact riser height, tread depth, stringer length and stair angle, with checks against IRC and IBC residential requirements.

The site offers more than 45 calculators covering standard, spiral, deck, winder, L-shaped, U-shaped, curved, floating, concrete and steel stairs, along with ADA layouts. Each one includes a live step-by-step visualization that updates as dimensions change. Users can switch between imperial and metric units and export a PDF plan with measurements and compliance status for a contractor or permit office.

What sets it apart is the published math. The site shows the formulas behind every result, including the Blondel comfort rule and the riser variation limit, so users can verify a figure by hand. It also includes a reference table of residential code limits and short guides on stair design. No sign-up is required.