A set of steps is where geometry meets the material order. The stair calculator settles the geometry — how many risers, what rise and run, how long the stringers — and the concrete calculator turns the pour into cubic yards, bag counts, and dry-mix weight. One is a layout tool; the other is a purchasing tool. For a concrete stair or stoop they are designed to be used in sequence, and each page points to the other for that workflow.
What each calculator does
The stair calculator takes total rise, a target riser height, and tread depth. It divides total rise by the target riser height and takes the nearest positive whole count as the number of risers. Actual rise is total rise divided by that count, total run is one fewer tread times the tread depth, and diagonal stringer length follows from the rise-and-run triangle. The page carries code context — it references the 2024 IRC, OSHA 1910.25, and the ADA stairways guide — but states plainly that target dimensions are inputs, not recommendations, and that the worksheet does not establish code compliance, headroom, landings, nosing, structure, or field fit.
The concrete calculator offers shape tabs for slabs, columns, tubes, curbs, and stairs. You enter dimensions, quantity, a waste allowance, bag yield, and bag weight. Shape volume is computed in cubic feet, waste is applied once, cubic yards is that adjusted volume divided by 27, bag count is the adjusted volume divided by the entered yield and rounded up to a whole package, and estimated dry-mix weight is the whole bag count times the entered bag weight. The 0.6 cubic foot yield and 80 pound weight shown initially are separate, editable planning assumptions, not universal product facts.
Side-by-side
| Stair calculator | Concrete calculator | |
|---|---|---|
| Primary question | How many risers, and what rise, run, and stringer length result? | How much concrete, how many bags, and what dry-mix weight? |
| Inputs | Total rise, target riser height, tread depth | Shape dimensions, quantity, waste, bag yield, bag weight |
| Key outputs | Riser count, actual rise, total run, stringer length | Cubic yards, cubic feet, whole bags, estimated dry-mix weight |
| Role in a stair project | Geometry and layout planning | Pour-volume and purchase planning |
| Geometry handling | Derives step geometry from total rise and target riser | Takes geometry as entered (including a stairs shape) for volume |
| Code stance | References code context; does not establish compliance | No structural or code claim; a geometric material estimate |
| Rounding | Counts rounded to whole risers; derived lengths to two decimals | Bags rounded up only after waste; yards to two decimals |
When to use which
Use the stair calculator when the question is layout: how many steps will fit a total rise, whether a target riser height produces an even count, how long the stringers need to be, and where the treads and risers land relative to code context. It is the tool to run before anything is formed or ordered.
Use the concrete calculator when the question is the pour: the volume a slab, column, tube, curb, or stair shape will take, how many bags to buy at the yield printed on the product, and what those whole bags will weigh. Its stairs shape estimates volume from the geometry you enter — so pair it with the stair calculator rather than expecting it to choose riser heights or tread depths.
Limits and disclaimer
Both pages are planning tools, not engineering approvals. The stair calculator’s targets are inputs rather than recommendations, and compliance, headroom, landings, structure, and field fit need qualified review under adopted codes. The concrete calculator’s bag yield and weight are editable assumptions — an 80 pound package does not have a universal yield — and its weight result is package count times package weight, not a concrete-density calculation. Product yield, subgrade, forms, spillage, reinforcement, placement, and structural requirements are separate considerations.