Concrete Stairs Volume Calculator
Calculate the cubic yards of concrete for a solid poured staircase from the step count, rise, run and width, plus bag counts.
How it works
side area = run × rise × [n(n+1) ÷ 2] · volume (cu ft) = (side area ÷ 144) × width · cubic yards = cu ft ÷ 27
A solid poured staircase is a stack of rectangles when viewed from the side: the bottom step is one rise tall, the next two rises tall, and so on, so the side-profile area is run × rise × (1 + 2 + … + n), which equals run × rise × n(n+1)/2. Multiply that cross-section (converted from square inches to square feet) by the stair width for the volume. This assumes a full solid pour against formed sides — an open stringer stair uses far less.
Worked example
Five steps, 7 in rise, 11 in run, 4 ft wide: n(n+1)/2 = 15, so side area = 11 × 7 × 15 = 1,155 sq in = 8.02 sq ft. Volume = 8.02 × 4 = 32.1 cu ft ÷ 27 = 1.19 cubic yards — about 54 eighty-pound bags, so order the ready-mix truck.
Frequently asked questions
Does this assume a solid pour?
Yes. The formula fills the full triangular block under the steps, which is how most exterior concrete stoops and porch stairs are cast against earth or form boards. Stairs built on open steel or wood stringers with individual treads use only a fraction of this volume.
What rise and run should I use?
A comfortable exterior stair is around a 6–7 in rise with an 11–12 in run, and code caps the rise near 7.75 in with a minimum tread near 10 in. Keeping every step identical is a safety requirement, not just a preference.
Should I add rebar?
Yes — poured stairs are typically reinforced with rebar or mesh tied into the footing so the nose of each tread does not crack off. Reinforcement does not change the concrete volume this calculator gives.
Related calculators
Estimates only — add for waste and confirm every load-bearing decision against local building codes and a design professional.