Stair Calculator

Stairs are governed by a simple idea: every step must be identical. You begin with the total rise, the vertical distance from one finished floor to the next, and divide it into a whole number of equal risers. That last word is the crux — a staircase with a slightly taller final step is a trip hazard, and building codes require risers to match closely, so the number of risers is chosen to make each one come out even. Comfort comes from the relationship between rise and going. A widely used rule is that twice the riser plus one tread should land near twenty-five inches: around seven-inch risers with ten-inch treads, or six-and-a-half with twelve. Steeper stairs feel abrupt and are hard to descend; shallower ones take up more floor space. The total run is the tread depth multiplied by the number of treads, which is one fewer than the number of risers because the top step lands on the floor above. Headroom and layout constrain the design more than the arithmetic. The run of the stair has to fit the available space, and the nosing, that small overhang at the front of each tread, adds to the effective depth without changing the structural cut. The stringer, the sloped beam that carries the steps, is the hypotenuse of the rise and run, and cutting its notches accurately is what makes the finished stair level and even. This calculator gives the number of risers, their height, treads, total run, stringer length and the resulting angle. It assumes a straight flight with no landing and a standard code-like geometry, and it does not cover railings or non-standard local requirements. Check your local building code before cutting, since permitted riser and tread dimensions are regulated.

This calculator returns estimates for planning and general information only. It is not engineering, architectural, structural, electrical or code advice, and it cannot replace a qualified professional who has seen the site. Material quantities depend on the actual dimensions, the product you buy and local building codes, so confirm the figures before ordering materials or starting work, and always follow local regulations.