Confirm rise and tread before volume
Small changes to riser height or tread depth can change both comfort and volume. Keep stair geometry consistent and check local code before placing forms.
concrete
Concrete Stairs Calculator
Estimate concrete for solid stair pours using width, tread depth, riser height, and step count.
Estimated stair concreteStair width, tread depth, riser height, and step count are required before the estimate appears.
Example4 ft wide x 11 in tread x 7 in riser x 5 steps
The estimate assumes a solid stair mass built from stacked step volumes.
Last reviewed: May 12, 2026 by the BuilderCalc editorial team.
SSR formula reference
Concrete Stairs Calculator formulas
These formulas are rendered in the server HTML so crawlers, LLMs, and users can read the method without running JavaScript. The interactive calculator can change the inputs, but the estimating math below is visible in the raw page source.
Volume (cubic feet) = Length x width x thickness (in inches / 12).
Volume (cubic yards) = Cubic feet / 27.
Bags (80-lb) = Cubic feet / 0.60, rounded up.
80-lb bag yields about 0.60 ft3, or 0.022 yd3.
| Result | Formula |
|---|---|
| Tread depth in feet | Tread depth in inches / 12 |
| Riser height in feet | Riser height in inches / 12 |
| Solid stair volume | Width x tread depth x riser height x step count x (step count + 1) / 2 |
| Cubic yards | Cubic feet / 27 |
Standard PSI by application
| Application | Recommended PSI |
|---|---|
| Patio or walkway | 3,000 PSI |
| Garage floor, residential | 3,500 PSI |
| Driveway, cars | 3,500 to 4,000 PSI |
| Driveway, trucks or RVs | 4,000 to 4,500 PSI |
| Foundations and footings | 3,000 to 4,000 PSI, per plan and code |
Bag yield reference
| Bag size | Common yield |
|---|---|
| 80-lb bag | About 0.60 ft3, or 0.022 yd3 |
| 60-lb bag | About 0.45 ft3, or 0.017 yd3 |
| 50-lb bag | About 0.375 ft3, or 0.0138 yd3 |
| 40-lb bag | About 0.30 ft3, or 0.011 yd3 |
Stair planning
Concrete Stairs Calculator planning notes
Concrete stairs need more planning than a flat slab because formwork, rise/run geometry, and edge support affect the pour.
Use a higher waste allowance
Stair forms have more edges, corners, and leakage risk than flatwork. A 10% to 15% allowance is often more realistic than a tight exact-volume order.
How to use it
Keep the estimate tied to field measurements
Measure stair geometry
Use stair width, tread depth, riser height, and step count from the actual form layout.
Check rise and run
Keep risers consistent and confirm tread/riser limits with local code before pouring.
Add waste for forms
Stair forms have more edges and leakage risk, so use a higher waste allowance than simple flatwork.
Related calculators
FAQ
Concrete estimating questions
How much concrete do I need for a 4-step stoop?
A typical 4-step stoop that is 4 ft wide with 10 inch treads and 7 inch risers needs about 0.4-0.6 cubic yards, or roughly 20-30 80 lb bags.
What is the maximum riser height for residential stairs?
The International Residential Code commonly limits residential stair riser height to 7.75 inches, with treads at least 10 inches deep. Local amendments can vary.
Do I need rebar in concrete stairs?
Outdoor stairs and stair runs over a few risers often need reinforcement such as #4 rebar in both directions. Confirm the final layout with local code or an engineer.
Can I pour concrete stairs in one pour?
Small stair sets under about five steps are often poured in one placement with rise-and-run forms. Larger stair runs may need staged forming or additional bracing.
What thickness should the stair slab be?
Solid concrete stairs are measured as the stair mass from tread surfaces down to the supporting base or footing. Edge footings may need to reach frost depth in cold climates.