Concrete steps tool
Concrete Stair Calculator
Set out poured concrete steps with equal risers and treads, then estimate the concrete volume for the flight — with a live section diagram and code-minimum guidance.
Finished floor to finished floor.
7-7.5in is comfortable; risers are equalised.
Horizontal depth, nosing excluded.
Plumb from the nosing line to the ceiling above.
Landings, stringers & handrail
Half-landings or quarter-turns in this flight.
16in suits most treads; 12in for thin or composite.
Measured above the nosing line.
4in (100mm) sphere rule.
Sets the bottom stringer drop.
Your flight
15 risers × 7.33in
14 treads at 10.50in / 26.7cm · 36.8 degree pitch
- Riser height (equal)
- 7.33in / 18.6cm
- Tread run (going)
- 10.50in / 26.7cm
- Total run
- 147.00in / 373.4cm
- Cut line (diagonal)
- 183.60in / 466.3cm
- Stringer stock length
- 195.60in / 496.8cm (16.3ft)
- Pitch
- 36.8 degrees
- 2R + G
- 25.17in / 63.9cm
- Stringers
- 4 at 12.0in centres (65.2ft stock)
- Handrail length
- 207.60in / 527.3cm (17.3ft)
- Balusters
- 39 at 5.2in centres
Code & comfort checks
IRC (US) allows a maximum 7.75in riser. Every riser in a flight must match within 3/8in.
Minimum going is 10.00in. Shallow treads are the single biggest cause of descending falls.
Comfortable domestic flights sit between 30 and 37 degrees; 42 degrees is the absolute ceiling.
Two risers plus one going should land between 24in and 25in (600-640mm) for a natural stride.
IRC (US) expects at least 36.0in of clear width above the handrail height.
Minimum headroom is 80in measured plumb from the tread nosing line.
IRC wants a graspable handrail 34-38in above the nosing line, continuous for the full flight, and no gap that passes a 4in sphere.
Guidance only — confirm against your local building control before you cut or pour.
Compare riser counts
| Risers | Riser | Going | Run | Pitch |
|---|---|---|---|---|
| 14 | 7.86in | 10.50in | 11.4ft | 38.9° |
| 15 | 7.33in | 10.50in | 12.3ft | 36.8° |
| 16 | 6.88in | 10.50in | 13.1ft | 34.9° |
The highlighted row is your current flight. Nudging the riser count is usually the cheapest way to bring a steep or shallow stair back inside code.
Advanced layout
Mark-out schedule, framing deductions & take-off
Quick answer
How do you calculate concrete stairs and the concrete needed?
Set out concrete steps the same way as any staircase — divide total rise by a target riser (commonly 6 to 7.5in for exterior concrete) to get a whole number of risers, then divide back for the exact height, with treads one fewer if the top step meets a landing slab. Estimate concrete volume by treating the stepped section as a stack of rectangular prisms: each step's volume is its rise times its run times the flight width, summed over every step, then add the volume of any structural slab or footing underneath.
- Set out risers and treads exactly as for any staircase.
- Exterior concrete steps often use a shallower 6-7.5in riser with an 11-12in tread.
- Volume per step = rise x run x flight width, summed over all steps.
- Add the footing or structural slab volume underneath the steps.
- Convert cubic feet to cubic yards by dividing by 27 for ordering.
- Always allow 5-10% extra concrete for formwork loss and an uneven subgrade.
Concrete steps use the same geometry, different targets
A poured concrete staircase follows the same rise-and-run arithmetic as a timber flight — total rise divided by a whole number of risers gives an equal riser height, and treads are sized from the total run. What changes for concrete is the comfortable target: exterior steps are commonly built with a shallower 6 to 7.5in riser and a deeper 11 to 12in tread than an interior stair, partly for comfort in wet weather and partly because the formwork is easier to build at a gentler pitch.
| Total rise | Risers | Riser height | Treads | Tread run | Est. volume (36in wide, cu yd) |
|---|---|---|---|---|---|
| 18in / 457mm | 3 | 6.00in | 2 | 11.00in | 0.14 |
| 24in / 610mm | 4 | 6.00in | 3 | 11.50in | 0.20 |
| 36in / 914mm | 5 | 7.20in | 4 | 11.00in | 0.28 |
| 48in / 1219mm | 7 | 6.86in | 6 | 11.50in | 0.44 |
| 60in / 1524mm | 8 | 7.50in | 7 | 11.00in | 0.55 |
Know your numbers in 30 seconds
Enter your step count, tread depth and riser height — the stair runner calculator gives you the exact length to order, in metres and feet, with waste included.
Open the stair runner calculatorWorking out concrete volume for a flight
Picture the finished stair as a stack of solid rectangular blocks, one per step, each shrinking by one riser and run from the block below. The bottom step carries the full height of the flight above it; the top step is a single tread thick. Volume per step is riser height x tread run x flight width; sum every step, then add the slab or footing underneath. For a 3-step flight, 36in wide, with 6in risers and 12in treads: step 1 is 6 x 12 x 36 = 2,592 cubic inches, step 2 adds another 2,592, step 3 adds 2,592 — total 7,776 cubic inches, or 4.5 cubic feet, before the footing.
- Convert cubic inches to cubic feet by dividing by 1,728.
- Convert cubic feet to cubic yards by dividing by 27 — most concrete is ordered by the yard.
- Add the footing or slab volume separately: width x depth x thickness.
- Round up to the nearest quarter or half yard when ordering ready-mix, since most suppliers have a minimum load.
Formwork and code notes
Concrete formwork needs to be built to the exact riser and tread dimensions worked out above, since concrete cannot be trimmed after it cures the way a timber stringer can be re-cut. Build in a light broom-finish slope of roughly 1/8 to 1/4in per foot across each tread for drainage, and keep the code's minimum run and maximum riser as hard limits on the form dimensions — hedge on the side of a slightly shallower riser and deeper tread if you are unsure, since a too-tall riser is a common source of inspection failures on exterior steps.
Footings and frost lines are a local decision
How deep a footing needs to go, and whether the steps can bear directly on compacted gravel or need a full frost-depth footing, depends entirely on local soil and climate. Treat any volume or thickness figure here as a starting estimate and confirm the structural detail with your local building department or a contractor before pouring.
From concrete rough-in to finished surface
If the finished concrete stair will later be carpeted or have a runner fitted over it, the riser height, tread run and nosing worked out here feed directly into the home page's stair runner calculator and stair runner length calculator, and the stair runner on concrete or tiled stairs guide covers how fixing methods differ from a timber stringer. For interior timber stairs built to a similar rise and run, the stair calculator adds the diagonal cut line and mark-out schedule a carpenter would use instead of formwork.
Whatever you decide, get the numbers first: the stair runner calculator doubles as a stair runner length calculator, adding nosing wrap, landings, winders, pattern repeat and waste so you order the right length the first time.
Frequently asked questions
How do I calculate concrete needed for steps?
Treat the flight as a stack of rectangular slabs. Each step's volume is its riser height x its tread run x the flight width. A 7in riser, 11in run and 36in wide step is 7 x 11 x 36 = 2,772 cubic inches, or about 1.6 cubic feet. Sum that across every step, add the footing slab underneath, convert cubic feet to cubic yards by dividing by 27, then add 5-10% waste.
What is the standard rise and run for concrete steps?
Exterior concrete steps are commonly built a little shallower than interior timber stairs — a 6 to 7.5in riser with an 11 to 12in tread run is typical for comfort and drainage, though the same IRC 7 3/4in maximum riser and 10in minimum run generally still apply as the outer limit. Always check your local code before pouring.
How thick should a concrete slab be under exterior steps?
A structural slab or footing under a concrete stair is commonly 4 to 6in thick over compacted gravel, though frost-prone regions typically require footings poured below the local frost line rather than a shallow slab — that is a structural and local-code decision, not something this calculator can substitute for.
Do concrete steps need rebar?
Most codes and most concrete contractors reinforce exterior steps with rebar or welded wire mesh to control cracking, particularly where the steps free-stand rather than bear on solid ground. Reinforcement detailing is project-specific and is generally worth confirming with a local contractor or engineer rather than assumed from a generic rule of thumb.
How do I work out riser and tread count for concrete steps?
Exactly as for timber stairs: divide the total rise by a target riser height, round to a whole number, then divide the rise back by that count for an equal riser. The same code minimums for run and maximums for riser height generally apply, though many installers favour a shallower riser for a poured exterior stair for wet-weather grip.
Can I calculate curved or radius concrete steps here?
This calculator handles straight, rectangular-flight geometry. Curved and radius steps need the same rise-and-run logic per step but with a varying run around the curve, which is a specialist forming job — use the straight-flight numbers here as your riser and going baseline, then take the radius layout to a mason or engineer.
How much extra concrete should I order for steps?
A common rule of thumb is 5-10% over the calculated volume to cover formwork seepage, an uneven or over-excavated subgrade, and spillage — smaller pours proportionally need a bigger safety margin because a short truck load on a small step job is a bigger problem than the same shortfall on a large slab.
Is the concrete stair calculator free?
The riser, tread, run, pitch and diagram are free with no account. A free account adds a surface-area take-off across the whole flight, useful for estimating a broom finish or a tile overlay once the concrete has cured.
Related tools & guides
Start with the numbers: our stair runner calculator also works as a stair runner length calculator, adding nosing wrap, landings, winders, pattern repeat and waste so you order the right length first time.