Concrete Stair Calculator

Pouring concrete stairs is one of the trickier residential concrete projects because the volume is not a simple box shape. Each step sits on top of the accumulated concrete below it, meaning the bottom step contains far more material than the top step. This calculator accounts for that stacking geometry so you get an accurate volume estimate. Standard residential stair dimensions follow building code requirements. The most common step rise is 7 to 7.75 inches and the most common run is 10 to 11 inches. The International Residential Code requires a maximum rise of 7.75 inches and a minimum run of 10 inches. All steps in a single flight must be uniform in both rise and run, with a maximum variance of 3/8 inch between the tallest and shortest step. Stair width depends on your application. Exterior entry stairs are typically 36 to 48 inches wide. Side yard utility stairs can be as narrow as 36 inches. Wide front porch stairs may be 5 to 8 feet across for a grander appearance. Building the formwork is the hardest part of concrete stairs. You need side forms cut to the stair profile shape, riser boards across the front of each step, and a solid base form underneath. Use 2x8 or 2x10 lumber for the riser boards and 3/4-inch plywood for the side forms. Brace everything heavily because wet concrete is extremely heavy and will blow out weak forms. Rebar is strongly recommended for concrete stairs. Run horizontal bars along the length and tie vertical bars at each riser location. The rebar cage should sit about 2 inches from all surfaces. Pour from the bottom step up and use a stiff mix with low slump so the concrete holds its shape on the angled riser faces.