Concrete Steps Calculator
Quick answer: Each solid step is a triangular profile: per-step volume = ½ × riser height × tread depth × step width (converted to cubic feet), multiplied by the step count plus a waste allowance. Example: 4 steps at 11-in tread, 7-in riser, 48-in wide = 4.28 cu ft (0.158 cu yd); with 10% waste, 4.71 cu ft → 8 eighty-lb bags (rounded up).
Enter the number of steps, tread depth, riser height, and step width to get per-step volume, total cubic feet and cubic yards, and the number of bags needed — rounded up, with your waste allowance included. Instant recalculation as you type.
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Your results
Solid-step estimate with waste allowance. Bag counts are rounded up. Buy one extra bag for small jobs.
How to use this calculator
Measure tread depth (the horizontal surface of each step), riser height (the vertical face), and step width in inches, then enter the number of steps. Pick the bag size you plan to buy and set a waste allowance — 10% is the default for clean forms.
Bag counts are rounded up: you cannot buy a partial bag, and running short mid-pour creates a cold joint that weakens the steps.
How this is calculated
Definitions: riser = step rise in inches, tread = step run in inches, width = step width in inches, 1 cu ft = 1,728 cu in, 1 cu yd = 27 cu ft.
- Per-step volume (cu in) = ½ × riser × tread × width (triangular profile of a solid step)
- Per-step volume (cu ft) = per-step cu in ÷ 1,728
- Total volume (cu ft) = per-step cu ft × number of steps
- Volume with waste = total × (1 + waste%)
- Total cubic yards = total cu ft ÷ 27
- Bags needed = ceiling(volume with waste ÷ yield per bag)
Assumptions: steps are fully solid (no hollow core); all steps identical; bag yields per the 2026 manufacturer table below. Estimates for material planning, not structural engineering.
Worked example
4 steps, 11-in tread, 7-in riser, 48-in wide: per-step volume = ½ × 7 × 11 × 48 = 1,848 cu in = 1.069 cu ft. Total = 1.069 × 4 = 4.28 cu ft = 0.158 cu yd. With 10% waste: 4.28 × 1.10 = 4.71 cu ft; 4.71 ÷ 0.6 = 7.84 → 8 eighty-lb bags.
Reference data
| Bag size | Yield per bag |
|---|---|
| 80 lb | 0.6 cu ft |
| 60 lb | 0.45 cu ft |
| 40 lb | 0.3 cu ft |
Source: Quikrete product specifications (2026).
Method & sources
The triangular-profile volume is exact geometry (½ × base × height × length); unit conversions use the exact constants 1,728 cu in per cu ft and 27 cu ft per cu yd. Bag yields are published manufacturer figures from Quikrete's 2026 product specifications. The waste percentage is a planning estimate labeled as such.
Frequently asked questions
Does this calculator assume solid or hollow steps?
Solid steps. Each step is modeled as a solid triangular profile: volume = 1/2 × riser height × tread depth × step width. If you are forming steps over an existing solid base or using a hollow-block core with a concrete cap, the actual concrete needed will be less — this calculator gives the full solid volume.
Why add a waste allowance to concrete?
Forms are never perfectly exact: lumber bows, ground settles, and some concrete stays in the mixer or spills. A 10% waste allowance covers these losses so you do not run short mid-pour, which matters because a partial pour can leave a cold joint that weakens the steps. For uneven subgrade or complex forms, consider 15%.
Which bag size should I choose?
The 80-lb bag is the best value per cubic foot (about 0.6 cu ft per bag) but weighs more to handle. The 60-lb bag (about 0.45 cu ft) and 40-lb bag (about 0.3 cu ft) are easier to lift and mix by hand. Total cost works out nearly the same per cubic foot across sizes — choose based on how many bags you are willing to lift and whether you are mixing by hand or in a mixer.
When should I order ready-mix instead of bags?
Bags make sense up to roughly 1 cubic yard (about 45 eighty-lb bags). Beyond that, the labor of mixing dozens of bags can outweigh the convenience of a ready-mix delivery. As a planning guideline: more than 30 bags is worth pricing out a short-load ready-mix truck.