Stair Calculator with Landing

A landing breaks a staircase into two flights, and each flight then needs its own run and its own stringer while every riser in the stairway stays the same height. Enter the total rise, a target riser, a tread depth and where you want the landing and this returns the riser height, the split of risers either side, both stringer lengths, the footprint for a straight, L-shaped or switchback layout, and a check against the 151 inch limit the IRC puts on rise between landings. A second tab works backwards from a landing height fixed by a threshold or a beam, finding the riser count that lands closest to it. A scale elevation is drawn so a miscounted tread is visible rather than buried.