Lay out a stair or ramp that actually works. Enter a floor-to-floor height and the tool sizes the risers and treads, builds the flight (straight, L, U or switchback with landings), and checks it against the rules — riser range, going, the 2R+G comfort rule, headroom, and ramp slope/landings — flagging anything out of bounds before you draw it up.
Runs entirely in your browser — nothing is uploaded. Orbit the 3D stair, and export an OBJ for Rhino or an SVG plan + section sized in millimetres.