Concrete Stairs Calculator
Find the concrete volume needed for a solid poured staircase from the number of steps, rise, run, and width.
📖 What is a Concrete Stairs Calculator?
A concrete stairs calculator finds the volume of concrete needed to pour a solid staircase, given the number of steps and each step's rise and run. It converts that volume into cubic yards for ready-mix ordering and into premixed bag counts, and shows a side-profile diagram of the stepped shape along with a per-step breakdown table.
Poured concrete steps are common at house entrances, porches, basement walkouts, decks, and garden or landscape stairs. Unlike a slab or a footing, a stair is not a simple rectangular volume: each step sits on top of, and is supported by, the concrete of every step below it, so the total shape is a stepped wedge rather than a flat block. Getting the volume estimate right avoids both an under-ordered truck and an expensive oversized one.
The stepped shape is why the formula includes a triangular-number term, N(N+1)/2, rather than simply N. Picture the staircase built up in horizontal layers, one rise thick: the bottom layer runs the full length under every step, the next layer up runs under one fewer step, and so on until the top layer, which only runs under the top step. Summing those shrinking layers gives the N(N+1)/2 pattern, the same one used to add 1 + 2 + 3 + ... + N.
This calculator handles the staircase itself. For a flat landing at the top of a flight, use the Concrete Calculator's Slab mode and add its volume to this one's result for the full pour.
📐 Formula
📖 How to Use This Calculator
Steps
💡 Example Calculations
Example 1 - 5 step entrance staircase
Example 2 - 3 small porch steps
Example 3 - 8 step deck staircase
❓ Frequently Asked Questions
🔗 Related Calculators
How do I calculate concrete volume for stairs?
For a solid stair, Volume = width x rise x run x N(N+1)/2, where N is the number of steps, and rise and run are each converted to feet. A 5 step stair with a 7 inch rise, 11 inch run, and 3.5 foot width needs about 28.1 cubic feet, or 1.04 cubic yards.
Why does the formula use N(N+1)/2 instead of just multiplying by N?
A solid staircase is not a uniform block; the bottom step is filled under the full run of every step above it, while the top step only fills its own tread. Stacking these unequal step layers works out to N(N+1)/2 times one rise-by-run layer, the same triangular-number pattern used to sum 1+2+3+...+N.
What is a comfortable stair rise and run?
A widely used rule of thumb is 2 x rise + run should equal 24 to 25 inches. Common residential exterior steps use a 6 to 7 inch rise with a 11 to 12 inch run. Always check your local building code, which typically sets maximum rise and minimum run limits.
How much concrete do 3 small porch steps need?
For 3 steps with a 6 inch rise, 12 inch run, and 4 foot width, the volume works out to 4 x 0.5 x 1 x 6 = 12 cubic feet, or about 0.44 cubic yards, around 27 bags of 60 lb concrete.
Should stair rise be the same for every step?
Yes, building codes require uniform rise and run within a single flight of stairs, with only small tolerances (often under 3/8 inch variance) allowed between steps. This calculator assumes every step has the identical rise and run you enter.
Do I need reinforcing steel in concrete stairs?
Poured concrete stairs typically use reinforcing bar or welded wire mesh to control cracking and add tensile strength, especially for stairs that span over a void rather than sitting on solid, compacted fill. Consult a structural engineer or your local code for the reinforcement schedule; this calculator estimates only the concrete volume.
How is stair volume different if the stairs are hollow underneath?
This calculator assumes a fully solid stair down to the base. If your stairs are formed with a hollow void beneath the treads (common for taller flights to save material), subtract the void's volume from this calculator's solid-stair result to get the actual concrete needed.
How many bags of concrete for a set of steps?
Divide the total volume in cubic feet by the bag yield: about 0.45 cubic feet for a 60 lb bag or 0.6 cubic feet for an 80 lb bag. An 8 step stair with a 7.5 inch rise, 10 inch run, and 3 foot width (56.25 cubic feet) needs about 125 bags of 60 lb concrete.
What stair width should I use for a standard exterior staircase?
Residential exterior stairs are commonly 3 to 4 feet wide for a single-person walkway, and wider (5 feet or more) for a main entrance or accessible route. Check your local code for minimum egress widths on stairs serving a required exit.
How do I calculate concrete for a stair landing?
A stair landing is a flat slab, not a stepped shape. Calculate it separately using the Concrete Calculator's Slab mode with the landing's length, width, and thickness, then add that volume to this calculator's stepped-stair volume for the total pour.