Staircase Calculator

About this calculator

Laying out a staircase starts from the total rise — the full floor-to-floor height — and works out how many steps are needed to climb it comfortably. Dividing the total rise by a target riser height gives the number of risers, which is always one more than the number of treads, since the top floor itself counts as the final step. Most building codes call for a riser height around 17-18 cm (about 7 inches) and a tread depth around 25-28 cm (about 10-11 inches), and stair designers often check the classic comfort rule of 2 × riser + tread ≈ 63 cm (about 25 inches), a guideline for a rise-and-run combination that neither cramps nor overextends a natural walking stride.

Once the number of steps and the tread depth are set, the stringer — the diagonal board that treads and risers attach to — is simply the hypotenuse of a right triangle whose legs are the total rise and the total run, found with the Pythagorean theorem. Builders, DIY renovators, and carpenters use this calculation before cutting stringer material or ordering pre-fabricated stair stringers, since getting the riser count wrong even by one step throws off every measurement afterward.

Enter the total rise, your target riser height, and the tread depth, and the calculator returns the riser and tread count along with the stringer length.