Concrete Stairs Volume Calculator
Estimate how much concrete you need to pour a staircase. Enter the number of steps, riser height, tread depth, and stair width to get the required concrete volume in cubic yards.
Estimate Concrete for Staircase Pour
Concrete Stairs Volume Formula
Where:
- \(n\) — number of steps
- \(t\) — riser height of each step (in)
- \(r\) — tread depth of each step (in)
- \(w\) — width of the staircase (in)
- \(c\) — concrete volume (yd³)
A solid staircase is a stack of rectangular blocks: the bottom step is one riser high, the second is two risers high, and the top step is \(n\) risers high. Since \(1 + 2 + \dots + n = \frac{n(n+1)}{2}\), only the four input dimensions are needed. All measurements are entered in inches, and the constant 93,312 (= 2 × 46,656 in³ per cubic yard) converts the result directly to cubic yards.
Concrete Stairs Volume – Calculation Example
Example: a straight staircase with 10 steps, a 7 in riser, an 11 in tread, and a width of 36 in (3 ft) — the calculator's default values.
\[ c = \frac{7 \cdot 11 \cdot 36 \cdot 10 \cdot 11}{93\,312} = \frac{304\,920}{93\,312} \approx 3.27\ \text{yd}^3 \]
Result: about 3.27 cubic yards (88.2 ft³) of concrete for the steps themselves. With a 10 % allowance for waste and spillage, you would order roughly 3.6 yd³.
How to Use the Calculator
- Enter the total Number of steps in the staircase.
- Enter the Height per step — the riser height in inches (comfortable stairs typically use 6–7.5 in).
- Enter the Depth per step — the tread depth in inches, measured from the front edge of a step back to the next riser (typically 10–11 in).
- Enter the Stairs width in inches, measured across the staircase.
- Read the Concrete Volume result, given in cubic yards.
What the Result Means
The result is the net volume of concrete in a solid, cast-in-place staircase: every step is assumed to be a full-depth block sitting on the one below it, with a stepped underside. This is the standard model for stairs poured against formwork that follows the step profile, and it is also a safe (slightly generous) estimate for stairs cast on a sloping slab.
An accurate volume estimate matters because ready-mix concrete is ordered by the cubic yard, often with a minimum truckload and extra charges for small loads. Running short mid-pour forces a cold joint that weakens the stair, while ordering too much wastes money. If you are mixing on site rather than ordering ready-mix, the Concrete Ingredients calculator and the Concrete Mix Ratio calculator help you translate this volume into cement, sand, and gravel quantities.
To plan a full pour, add the stairs to the volumes of any other elements — slabs, footings, walls — using the Concrete Yardage calculator, and order the combined total plus a 5–10 % contingency for waste, spillage, and uneven subgrade.
Assumptions and Limitations
- Uniform steps: every step must have the same riser and tread; stairs with varying step sizes or a curved plan need a manual takeoff.
- Steps only: landings, platforms, and the slab or footing at the base are not included — estimate those separately with the Concrete Footing/Slab Pours calculator.
- Solid section: the model assumes a solid cast; precast stairs or hollow-core designs use less concrete.
- No deduction for reinforcement: rebar and mesh displace only about 1–2 % of the volume and are safely covered by the waste allowance.
- Units: all inputs are in inches; if your drawings are metric, convert first (1 in = 25.4 mm).
A quick comfort check while you are at it: many building codes follow the "7-11" guideline (7 in riser, 11 in tread), and the rule of thumb \(2t + r \approx 24\text{–}25\) inches usually produces a comfortable stride.
Typical Volumes for Common Staircases
| Steps | Riser (in) | Tread (in) | Width (in) | Volume (yd³) |
|---|---|---|---|---|
| 4 | 7 | 11 | 36 | 0.59 |
| 8 | 7 | 11 | 36 | 2.14 |
| 10 | 7 | 11 | 36 | 3.27 |
| 12 | 7 | 11 | 48 | 6.18 |
Note how fast the volume grows: doubling the number of steps nearly quadruples the concrete, because the average height of the stacked blocks rises along with the count. Tall staircases are worth estimating carefully — and worth a second look at your order before the truck arrives.
Frequently Asked Questions
How do I calculate the concrete volume of stairs by hand without the formula?
Treat the stair profile as a right triangle: multiply the total rise by the total run and divide by 2 to get the cross-section area, then multiply by the width in feet and divide by 27 for cubic yards. For example, a staircase rising 70 in over a 110 in run is about \(5.83 \times 9.17 / 2 \approx 26.7\ \text{ft}^2\); times a 3 ft width that is 80 ft³, or about 3 yd³. This triangle shortcut matches the step-stack method for uniform stairs.
How many 80-lb bags of concrete mix do I need for stairs?
An 80-lb bag of bagged mix yields roughly 0.6 ft³ of concrete, so one cubic yard (27 ft³) takes about 45 bags. A 3.27 yd³ staircase would need nearly 150 bags — that is a lot of mixing, and stair pours must happen in one continuous session to avoid weak cold joints. For anything beyond two or three steps, ready-mix delivered by truck is usually the more practical and safer choice.
Does pouring stairs on an existing slab or slope use less concrete?
Yes. This calculator assumes a solid, form-built stair where each step is a full block. If the stairs are poured against a sloping slab or compacted fill that already follows the step profile, the concrete only fills the stair shell, not the solid wedge underneath. In that case your true volume is noticeably smaller — treat this calculator's result as a generous upper-bound estimate and check the shell thickness separately.
How do I convert the result to cubic meters or cubic feet?
Multiply cubic yards by 27 to get cubic feet, or by 0.765 to get cubic meters. For example, 3.27 yd³ is about 88 ft³ or 2.5 m³. If your drawings are metric, first convert millimeters to inches by dividing by 25.4 before entering values — the inputs must be in inches for the result to be correct.
What riser and tread sizes are safe and code-compliant?
Most residential building codes allow risers of about 4–7.75 in and require treads of at least 10 in, with the 7-11 combination (7 in riser, 11 in tread) being the classic standard. The comfort rule \(2t + r \approx 24\text{–}25\) inches works well for a natural stride. Check your local code before finalizing dimensions, since stair geometry is strictly inspected and oversized risers can fail inspection.
What are common mistakes when measuring stairs for concrete?
The biggest errors are measuring the tread including the nosing overhang (use the actual tread depth from riser to riser), forgetting that the top step often lands flush with the floor so you count one fewer riser, and neglecting the footing or base slab, which this tool does not include. Also verify every riser is truly uniform — a staircase with an uneven first or last step is a frequent trip hazard and a code violation.
Should I add concrete for the landing and the base slab?
Yes, if your design has them. This calculator covers the steps only, so estimate any mid-stair landing as a simple slab (length × width × thickness) and the base footing separately, then add all volumes together before ordering. A landing can add a significant amount of concrete — a 4 ft × 4 ft landing, 6 in thick, is 8 ft³ (0.3 yd³) by itself.