Concrete Stairs Volume Formulas
\[\text{Tread (ft)} = \frac{\text{Tread (in)}}{12}, \quad \text{Riser (ft)} = \frac{\text{Riser (in)}}{12}\] \[\text{Steps Volume (cu ft)} = \text{Width (ft)} \times \text{Tread (ft)} \times \text{Riser (ft)} \times \frac{N(N+1)}{2}\] \[\text{Landing Height (ft)} = N \times \text{Riser (ft)}\] \[\text{Landing Volume (cu ft)} = \text{Width (ft)} \times \text{Landing Depth (ft)} \times \text{Landing Height (ft)}\] \[\text{Total Volume (cu yd)} = \frac{\text{Steps Vol (cu ft)} + \text{Landing Vol (cu ft)}}{27} \times 1.10\] \[\text{80 lb Bags Needed} = \left\lceil \frac{\text{Total Cu Ft} \times 1.10}{0.60} \right\rceil\]Solid Concrete Stairs Material Reference Table (7” Riser, 11” Tread, 80lb Bags)
| Number of Steps | Staircase Width | Top Landing Depth | Total Height | Concrete Volume (+10%) | 80 lb Bags Needed | Bagged Material Cost ($6.50/bag) | Ready-Mix Equiv. Cost ($140/yd) |
|---|---|---|---|---|---|---|---|
| 3 Steps | 3 feet wide | 2 feet landing | 21 inches | 0.61 cu yds | 31 bags | $201.50 | $85.40 |
| 4 Steps | 4 feet wide | 3 feet landing | 28 inches | 1.25 cu yds | 62 bags | $403.00 | $175.00 |
| 5 Steps | 4 feet wide | 3 feet landing | 35 inches | 1.83 cu yds | 91 bags | $591.50 | $256.20 |
| 6 Steps | 5 feet wide | 4 feet landing | 42 inches | 3.32 cu yds | 165 bags | $1,072.50 | $464.80 |
Step-by-Step Guide: How to Calculate Concrete for Steps
- Count Number of Risers: Count total vertical steps required to reach porch or entrance threshold.
- Determine Tread & Riser Dimensions:
- Standard comfortable steps use 7 inch risers and 11 inch treads.
- Include Top Entrance Platform: If pouring a porch slab monolithically with the steps, enter the landing depth in feet.
- Choose Mixing Method:
- Under 1.5 cu yds: Mix 80 lb bags on-site using a portable drum mixer.
- Over 1.5 cu yds: Order ready-mix concrete truck delivery to eliminate hand mixing dozens of heavy bags.
Frequently Asked Questions
How much concrete do I need for a 5-step staircase?
A 5-step solid concrete staircase (7 in riser, 11 in tread, 4 ft wide) with a 3 ft top landing requires approximately 1.83 cubic yards (49.5 cubic feet) of concrete, or 91 bags of 80 lb concrete.
How do you calculate concrete volume for stairs?
Step Volume (cu ft) = Width (ft) × [Tread (in) / 12] × [Riser (in) / 12] × [N × (N + 1) / 2], where N is the number of steps. Platform Volume = Width (ft) × Landing Depth (ft) × Total Height (ft).
How many 80lb bags of concrete make a cubic yard?
It takes 45 bags of 80 lb concrete to equal 1 cubic yard (27 cubic feet) of mixed concrete.
Is it cheaper to use pre-mixed bags or order ready-mix concrete for stairs?
For small staircases under 1 cubic yard (under 45 bags), pre-mixed bags ($200–$300) are usually cheaper than paying short-load delivery fees ($150–$200 extra) for ready-mix trucks. For larger staircases over 1.5 cubic yards, ready-mix is faster and less labor intensive.
What is standard riser height and tread depth according to building codes?
IRC building codes specify a maximum riser height of 7.75 inches (7 inches standard) and a minimum tread depth of 10 to 11 inches.
Do outdoor concrete stairs require rebar?
Yes. Concrete stairs require #4 rebar cages pinned into foundation footings or porch walls to prevent settling, cracking, or tipping forward.
Is my personal data saved anywhere?
No. All calculation logic runs strictly inside your local browser.