How this calculator works
Solid steps are treated as a stack of blocks that each run down to the ground. The bottom step is one riser tall, the next is two risers tall, and so on; the top landing is the full height. Adding these blocks gives the total volume.
Steps (k = 1 … n−1) = Width × Tread × Riser × (n−1)·n ÷ 2
Landing = Width × Landing depth × n × Riser
Total = (Steps + Landing) × (1 + Waste%/100)
Assumptions and tips
- Bag yields follow the manufacturer’s published figures: 80 lb ≈ 0.60 cu ft, 60 lb ≈ 0.45 cu ft, 50 lb ≈ 0.375 cu ft, 40 lb ≈ 0.30 cu ft.
- Bag counts are always rounded up to whole bags.
- The waste allowance covers spillage, uneven subgrade and over-excavation. 5–10% is common; use more for irregular forms.
- Assumes solid steps. Steps poured over fill or against a wall use less concrete.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| Number of risers | 3 |
| Step width | 4 ft |
| Riser height | 7 in |
| Tread depth | 11 in |
| Top landing depth | 36 in |
| Waste allowance | 10 % |
| Bag size | 80 lb bag (0.60 cu ft) |
| Result | Value |
|---|---|
| Concrete needed | 1.12 cubic yards |
| 80 lb bags | 51 bags |
| Volume (with waste) | 30.2 cu ft |
| Total height | 21 in |
| Total run including landing | 58 in |
Step by step:
- Steps below the landing: 4 × 0.917 × 0.583 × (2×3÷2) = 6.42 cu ft
- Landing: 4 × 3 × 3 × 0.583 = 21 cu ft
- Total with 10% waste = 30.16 cu ft = 1.117 yd³
- Bags = 30.16 ÷ 0.6 → 51
Concrete for typical entry steps
4 ft wide, 7 in risers, 11 in treads, 10% waste.
| Risers & landing depth | Concrete needed | 80 lb bags |
|---|---|---|
| 2 risers, 36 in landing | 0.66 cubic yards | 30 bags |
| 3 risers, 36 in landing | 1.12 cubic yards | 51 bags |
| 4 risers, 36 in landing | 1.66 cubic yards | 75 bags |
| 3 risers, no landing | 0.52 cubic yards | 24 bags |
Common mistakes to avoid
- Counting treads instead of risers — the landing step counts as a riser.
- Pouring solid when fill would do: big landings use most of the concrete.
Frequently asked questions
How many bags of concrete for 3 steps?
With the defaults (4 ft wide, 7 in risers, 11 in treads and a 36 in deep landing) you need about 1.1 cubic yards — 51 bags of 80 lb mix with 10% waste. Most of that is the landing; a shallower landing needs much less.
Can I reduce the concrete needed?
Yes. Builders often fill the core with compacted gravel or rubble, which can cut the concrete substantially. Subtract the fill volume from the result.