Concrete Stairs Calculator

Concrete volume, bags and ready-mix order for poured concrete stairs — any number of steps, with an optional top landing.

Stair geometry

in
IRC max 7¾″ (197 mm) residential.
in
IRC min 10″ (254 mm) residential.
ft
IRC min 36″ (914 mm).
in
Leave 0 for no landing (stairs go directly to upper floor).
%

Bag option

Bagged makes sense up to ~1.5 yd³ (≈ 67 × 80-lb bags).
$
Ready-mix price (NRMCA 2026 ≈ $140/yd³ at 3,000 PSI).

Calculation results

Concrete order amount

— yd³

Volume (raw)

— ft³

Bags needed

— bags

Total rise

— in

Order amount includes waste — that's what to spec on the delivery ticket. Bagged is convenient up to ~1.5 yd³; above that ready-mix is dramatically cheaper per yd³.

Informational only. Volume formula assumes solid-poured stairs without weight-saving voids. For complex stair geometry (curved, winder, cantilevered), break into sub-volumes and sum. For structural stairs (cantilevered, retaining wall integration), engineer-designed reinforcement is required.

Volume formula for poured stairs

Concrete stairs are stepped solids. Each step fills a rectangular volume from the floor up to that step's tread elevation. The formula sums these incremental volumes:

Vsteps = run × rise × width × N(N + 1) / 2
Vlanding = platform_depth × (rise × N) × width
Vtotal = Vsteps + Vlanding

Worked example — 5 steps, 7″ rise, 11″ run, 3 ft wide, no landing, 10 % waste

  • Total rise = 5 × 7 = 35″ (2.917 ft)
  • Vsteps = (11/12) × (7/12) × 3 × 5 × 6 / 2 = 0.917 × 0.583 × 3 × 15 = 24.06 ft³
  • Vlanding = 0 (no platform)
  • Raw volume = 24.06 ft³ = 0.891 yd³
  • With 10 % waste = 0.98 yd³
  • 80 lb bags (0.60 ft³ each): ⌈26.46 / 0.60⌉ = 45 bags

For an order under 1 yd³, ready-mix carries a short-load fee (typically $150). Bagged is roughly the same total cost but easier to schedule and pour for small jobs.

Frequently asked questions

How much concrete for 5 stairs?
A typical 5-step stair (7″ rise, 11″ run, 3 ft wide) needs about 24 ft³ = 0.9 yd³ of concrete. With waste that rounds to 1 yd³. Bagged option: about 45 × 80-lb bags.
How many bags of concrete for stairs?
Depends on stair count and dimensions. Rule of thumb: each step (7″ × 11″ × 36″ wide) needs about 1.2-1.5 × 80-lb bags. A 5-step stair = roughly 7-8 bags per step accumulated (volumes grow with each step). Always use the full calculator.
Can I use bags for concrete stairs?
Yes for small stairs (3-6 steps). Above that the labor of mixing dozens of bags outweighs the savings. Hire a ready-mix truck once total volume reaches 1-1.5 yd³ even with the short-load fee.
How thick should concrete stairs be?
For freestanding stairs, the volume formula assumes solid pour from grade up to each step. For wall-supported or cantilevered stairs, the structural slab is typically 6-8″ thick with #4 rebar grid — those need engineer-designed reinforcement.
Do I need a footing under concrete stairs?
Yes — concrete stairs need a frost-depth footing below the bottom riser. In northern states that is 42-48″; in southern states 12-18″. The footing prevents frost-heave from cracking the bottom of the stairs.
How long does it take concrete stairs to cure?
Walkable in 48 hours; final strip-form at 24-48 hours; full design strength at 28 days. In cold weather (< 50 °F) curing slows significantly — use blankets and curing accelerators if pouring below 40 °F.
What is the difference between this and the Staircase Calculator?
This calculator (Concrete Stairs) gives concrete volume and bag count for poured stairs. The other Staircase Calculator (in Framing & Carpentry) is for wood-framed stairs and computes riser height, tread depth and stringer length per IRC code. Different materials, different outputs.