Staircase calculators for people who build stairs
Give it a floor-to-floor height and get back every number you need: riser height, tread depth, total run, pitch, stringer length and a cut list — checked against the building code and drawn to scale.
Free, and no account needed. Sign up free only if you want to save projects. Works in feet and inches or millimetres.
What it does
Rise, run and everything after it
Riser height, tread depth, total run, pitch, stringer length — plus the two riser counts either side of the one it picked.
Or work backwards from the space
Give it the height AND the run you have to work with, and it reports every riser and tread combination that fits, ranked by code and comfort — or tells you plainly that no straight flight will, and what to do instead.
The numbers people get wrong
Finished floor thicknesses, the stringer drop at the bottom cut, the floor opening you need for headroom, and winder going measured on the walk line rather than the tread centre.
Save whole projects
The project planner puts every calculation for one stair on one page — code check, stringer cuts, floor opening, cut list and scaled drawings. Create a free account (email or Google) to save projects and come back to them.
Area and perimeter of any shape
A separate set of calculators for flat shapes — rectangles, triangles, circles, trapezoids, polygons and more — with the formula shown and a labelled drawing.
Checked against the code
Every result is tested against the IRC, the IBC or UK Approved Document K, with the section number beside each line, so you can see exactly what passes and what does not.
Built around the errors, not just the arithmetic
Most stair calculators stop at rise and run. The ones that matter on site are the next three: what happens to the first riser once the hardwood goes down, how long the hole in the floor has to be, and where exactly each baluster gets marked.
Start with your floor-to-floor height
That one measurement is enough to produce a full set of numbers and a scale drawing.