Concrete Steps Calculator
Risers and tread dimensions to yards and bags.
Also known as stair concrete · step volume · staircase concrete
With the default inputs: Number of steps 3 stages · Step width 4 ft · Tread depth 11 in etc.Concrete required 0.52 yd³
Use your own dimensions ↓Inputs
Result
| Net volume (solid) | 12.8ft³ |
| With waste | 14.1ft³ |
| Total rise | 21.0in |
| Total run | 33in |
| 80 lb bags | 24bags |
| 60 lb bags | 32bags |
| Total weight | 2047lb |
| Average riser height | 7.00in |
How this is worked out
Calculated as a solid poured stair: the first step is one riser high, the second two, and so on, which is why the volume is width x tread depth x sum of (step number x riser height) rather than a simple box. If the stair is built over fill or blockwork with only a concrete skin, actual concrete is far less and this figure overstates it - that detail has to be calculated from the topping thickness. Code-wise, risers in one flight should not vary by more than 3/8 in or people trip; exterior treads want at least 11 in, and in freezing climates add a non-slip finish.
Next up: Concrete Volume Calculator · Concrete Mix Design Calculator
Reverse: known result, work out one input
Enter a target result; the other inputs stay fixed and this one is worked out.
Formula
| Volume = width × tread × Σ(i × riser) | i = 1…steps, thickness grows each step |
| Σ(i) = N(N+1)/2 | grows quadratically with step count |
| Cubic yards = volume ÷ 27 | |
| Bags = volume ÷ bag yield | 80 lb 0.60 ft³, 60 lb 0.45 ft³ |
How to work it out
- Fix the total rise first: measure from the lower floor to the porch floor and divide by your target riser height to get the step count.
- Use a 6-7 in riser with an 11-12 in tread and check it against 2 x riser + tread = 24-25 in.
- Volume grows step by step: the first step is one riser high, the second two, and so on - not a single box.
- Add 10% waste, divide by 27 for cubic yards and by bag yield for bags.
- The footing is separate: steps must bear on a concrete footing below frost depth, not on fill.
Where it goes wrong
- Treating it as a box at average height - a stair is stepped and averages about half the total height, so this doubles the order.
- Bearing on fill or a brick pad - one winter of frost heave cracks it; that is settlement, not strength.
- Unequal risers within one flight - more than 3/8 in difference is the classic trip hazard on exterior steps.
Material and cost
A poured concrete stair including formwork, reinforcement, placing and finishing runs about USD 40-90 per step, so a three-riser porch stair is commonly USD 400-900 complete. Precast units run USD 250-600 for the set - cheaper but fixed in size and style. Concrete itself is USD 200-300 per cubic yard with a short-load premium, or USD 5-8 per 80 lb bag mixed on site. Labour is usually more than half the total.
On site
- Brace the formwork hard - concrete exerts real lateral pressure and a bulging form leaves a belly you cannot fix.
- Strip the side forms at 24 hours but keep off the steps for 7 days; full strength takes 28. Cover with plastic to cure.
- Fall the treads 1-2% to drain and form a drip groove at the nosing, or water tracks back under the step.
Basis
- IRC International Residential Code, Section R311.7 (riser height, tread depth and riser variation)
- ACI 332 Residential Code Requirements for Structural Concrete (thickness and reinforcement)
- ACI 318 Building Code Requirements for Structural Concrete
FAQ
What riser height and tread depth should I use?
How deep does the base need to be?
Does it need reinforcement?
Cite this page
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Building Calculator. Concrete Steps Calculator. 2026-10-25. https://jianzhujisuan.com/en/concrete-steps