Concrete Stairs Volume
Concrete for a straight flight, solid on grade or on a waist slab, from width, riser, tread and step count, plus a landing, waste and bags; formwork area too.
Steps, waist and landing volumes, the total with waste in yd³ or m³, bags from your yield, and the riser and stringer formwork area — geometry stated, stair limits not judged.
Example: Six 7 in × 11 in steps 4 ft wide, poured solid with a 4 ft landing 4 in thick, need 1.86 yd³ before waste (2.01 yd³ at 8 %) — about 91 bags at 0.6 ft³.
Steps as blocks,
or a slab under triangles.
The two pours and their geometry, the landing and formwork, and what is not judged.
Solid on grade
Each step is a block the full width, one riser high and as deep as all the treads above it, so the volumes form the series 1, 2, …, n treads: V = width × riser × tread × n(n + 1)/2. This is the usual pour against a slope or fill.
Waist slab
A suspended flight is a sloping slab (the waist) with triangular steps on top: steps = width × n × ½ × riser × tread; waist = width × slope length × thickness, slope length = √(rise² + run²). The waist thickness is yours; it is a design value.
Landing, waste, formwork
A landing is a slab of stair width × length × thickness. Waste is added at the end; bags follow from your bag yield. Formwork area = riser faces + two side profiles (the stepped area). Riser and tread are taken as typed — the Stair Calculator checks them against limits you enter. Nothing leaves the browser; the same four anonymous usage counts as the rest of the site apply.
SOURCES
- Solid geometry: stepped prism as the series n(n+1)/2 of riser × tread blocks; waist slab as a sloping prism plus triangular steps (standard mensuration)
Last reviewed 20 September 2026. How results are checked: How we verify.