How much concrete for steps
A concrete steps calculator adds up blocks: a solid set of steps is a staircase of rectangular blocks: the first tread sits on a block one riser high, the second on a block two risers high, and so on. Adding them up gives width × tread × riser × n(n − 1) ÷ 2 for n risers, plus a platform at the top if the steps meet a door. The calculator does that sum and converts it to cubic feet, cubic yards, litres and cubic metres.
- Ready-mix is ordered by the cubic yard or cubic metre; round up and add a little for an uneven base.
- Bagged concrete is sold by weight, but the bag prints its yield as a volume. Divide the volume here by that yield.
- Hollow steps (a fill of gravel or rubble under a sloped slab) take less concrete; this calculator assumes solid steps.
Concrete stairs: dimensions and the code
Concrete stairs and steps follow the same riser and tread rules as wood ones. Under the IRC, risers are at most 7-3/4 in and treads at least 10 in, every riser and tread in the flight within 3/8 in of the others[1]. Treads and landings may slope no more than 1:48 (2%), except that a landing that must drain may slope up to 1:20[1][2]. A slight front-to-back fall sheds water without breaking that rule.
| Total rise | Risers | Riser | Steps only | With platform |
|---|---|---|---|---|
| 14″ | 2 | 7″ | 2.1 cu ft | 0.6 cu yd |
| 21″ | 3 | 7″ | 6.4 cu ft | 1.02 cu yd |
| 28″ | 4 | 7″ | 12.8 cu ft | 1.51 cu yd |
| 35″ | 5 | 7″ | 21.4 cu ft | 2.09 cu yd |
| 42″ | 6 | 7″ | 32.1 cu ft | 2.74 cu yd |
Building the forms
Each riser gets a form board as wide as the stair and one riser high, ripped from 2x lumber. Bevel the bottom edge of each riser board so you can trowel the full tread, and brace the side forms against the pressure of wet concrete. The cut list in the results gives the number and height of riser boards; the side forms follow the stair profile in the diagram. Where the steps meet a deck instead of a slab, the deck stair calculator covers wood stairs, and the stair calculator compares codes.
Outside the US
England's private stair rules (rise 150–220 mm, going 220–300 mm) and Canada's (rise 125–200 mm, run 255–355 mm) apply to external steps too[4][3]. England also asks for a going of at least 280 mm on external tapered steps of dwellings[4]. Switch the panel to metric and pick the code to check a layout. For a long approach, a landing between flights keeps every flight within the limits.
Frequently asked questions
How does a concrete steps calculator work out the volume?
It adds one block per step: width × tread × riser × the step number, summed over all steps, plus the top platform. Divide cubic feet by 27 for cubic yards.
How much concrete do I need for 3 steps?
Three 7 in risers with 11 in treads, 48 in wide and no platform hold 48 × 11 × 7 × 3 = 11,088 cu in, about 6.4 cu ft or 0.24 cu yd.
What size should concrete steps be?
Under the IRC, risers up to 7-3/4 in and treads of at least 10 in, all equal within 3/8 in. Outdoors many builders use 6 to 7 in risers and 11 to 12 in treads.
Should concrete steps slope?
Only slightly. The IRC allows a stair walking surface to slope up to 1:48 (2%) so water can drain off the front of each tread.
How do I calculate concrete in cubic yards?
Work out the volume in cubic feet and divide by 27. In metric, cubic metres are the ordering unit.
Sources
- 2021 International Residential Code, Chapter 3: Building Planning (R301.5, R311.7 stairways, R312 guards)
- 2024 International Residential Code, Chapter 3 (R318.7 stairways, R320 handrails, R321 guards)
- National Building Code of Canada 2020, Division B, Part 9, Section 9.8 Stairs, ramps, handrails and guards
- Approved Document K: Protection from falling, collision and impact (2013 edition, for use in England)