Concrete stairs calculator
This estimates the solid stepped mass from the sizes you enter. It does not design the stair, its reinforcement or the slab that carries it, and it is not the building code's riser and tread limits. Pour to your drawings and check the order with your supplier.
Enter the step count, the riser and tread and the width, and the tool estimates the concrete in the solid stepped mass — every step a block one tread deep, standing on the ground — then converts it to yards, metres and bags.
Exemple détaillé
Five steps at a 7-inch riser and an 11-inch tread: the step heights add up to 1 + 2 + 3 + 4 + 5 = 15 risers. One riser × tread is 7 × 11 = 77 in² (0.535 ft²), so the side profile is 15 × 0.535 ≈ 8.02 ft²; at 3 ft wide that is 24.1 cubic feet, or 24.1 ÷ 27 ≈ 0.89 yd³ (0.68 m³). Add 10% and it is 0.98 yd³ — a 1 yd³ ticket, or 45 bags at 0.6 ft³.
In metric: five steps at a 180 mm riser and a 280 mm tread. One riser × tread is 0.18 × 0.28 = 0.0504 m², times 15 = 0.756 m²; at 0.9 m wide that is 0.680 m³ (0.89 yd³). Add 10% — 0.748 m³ — and the ticket reads 0.8 m³ at the tenth-of-a-metre rounding.
Sur le chantier
Porch steps with a landing. Four 7-inch risers up to a 4 ft × 4 ft landing, 4 ft wide, 11-inch treads. The fourth riser is the face of the landing, so the steps below it are three: 1 + 2 + 3 = 6 risers × 0.535 ft² × 4 ft = 12.8 ft³. The landing is a box the full height, 28 in (2.33 ft): 4 × 4 × 2.33 = 37.3 ft³. Together 50.2 ft³ = 1.86 yd³, and with 10% (2.04 yd³) the ticket reads 2.5 yd³ after the half-yard rounding. The landing is three times the steps — run it as its own box on the concrete page and add. In metric, three 180 × 280 mm steps 1.2 m wide are 6 × 0.0504 × 1.2 = 0.36 m³; a 1.2 × 1.2 m landing 0.72 m high is 1.04 m³; together 1.40 m³, 1.54 m³ with 10% — order 1.6 m³.
Fill under the steps. On a big set of steps the solid block is a lot of concrete doing nothing. Where the detail allows a compacted fill core, the pour is the steps minus the core: measure the core as its own box after the fill is in, and subtract. The tool gives you the solid figure to start from.
Steps against a slope. If the steps are cast on a bank, the block is thinner at the back than a free-standing set — the bank takes the place of concrete. Measure the actual depth at the top and bottom risers and average, then treat it as a slab of that thickness on the slope length. The stepped formula is for the free-standing case.
What went wrong?
Quick referencefor poured steps
- The steps
- riser × tread × steps × (steps + 1) ÷ 2 × width, all in feet (or all in metres)
- Why not ½ rise × run
- that ramp misses the nose of every step — short by 1 in (steps + 1)
- A landing
- its own box, the full height of the top step
- ft³ at 7 × 11, 3 ft wide
- grows faster than the step count — 4 steps 16.0 · 5 steps 24.1 · 6 steps 33.7 · 8 steps 57.8
- m³ at 180 × 280 mm, 0.9 m wide
- 4 steps 0.45 · 5 steps 0.68 · 6 steps 0.95 · 8 steps 1.63
- Unités
- 27 ft³ in a yard · 45 bags at 0.6 ft³
- Metric units
- 1 m³ = 1.31 yd³ · about 71 bags at 0.014 m³ · 1 yd³ = 0.765 m³
Waste & overagewhat to add, and why
- Formed steps are notorious for spillage — mix goes over the riser boards, the top step is over-filled and floated off — so crews add 10–15% here rather than the usual 10%. The waste field takes it.
- Steps poured against a slab or wall usually pour with that element; check the plant minimum before ordering half a yard on its own.
Mistakes to catchbefore you order
- Typing the finished stair width as the riser height, or the tread depth in inches into a field set to feet — the formula multiplies all three, so one wrong unit ruins the lot.
- Counting a deep top landing as a step in Number of steps: enter only the steps below a landing and figure the landing as its own box.
- Forgetting the fill under a tall flight — the figure here is solid concrete; if you are filling under it with rubble, the concrete is only the shell you form.
What an inspector looks forthe building inspector, twice — before the pour and again at final
On this part of the job
- Every riser measured, and every tread, then the biggest compared with the smallest. Consistency between steps is checked as strictly as the size itself.
- Rise and run against the limits in the adopted code — look them up, type them into the stair tool, and know your numbers before the form goes up.
- The bottom step: the run of the landing at the foot and whether the finished slab or paving will change the first riser once it is poured.
- Handrail and guard fixings where they have to be cast in or blocked out, because retrofitting an anchor into a cured step is nobody's favourite afternoon.
- Bearing and reinforcement under the flight, and how the steps are tied to the building or the landing.
Have this ready
- Your rise and run worked out and written on the form, including the finished-floor allowances at both ends.
- The stair section from the drawing.
- A level and a straight-edge long enough to bridge three treads.
Every figure an inspector measures against comes from the code your jurisdiction has adopted, the stamped drawing, or the manufacturer's printed instructions — so none of them are printed here. Look the number up in your own book, type it into the tool, and the arithmetic is yours.
La formule
volume = riser × tread × steps × (steps + 1) ÷ 2 × width
Step 1 is one riser tall, step 2 is two, and so on; each is one tread deep. The heights add up to steps × (steps + 1) ÷ 2 risers, so that many riser-by-tread rectangles make the side of the stair, and multiplying by the width sweeps it across. Feet cubed divide by 27 for yards; metric comes out in cubic metres directly (riser and tread go in as millimetres, so ÷ 1,000 first). Either way the other figure is shown beside it.
What this tool assumes
That the steps are solid to the ground, each one tread deep, the top step included. Riser, tread, width, waste and bag yield are all fields you set. The only baked figure is the 27-cubic-feet-per-yard definition.
Questions
- How do I calculate concrete for stairs?
- Solid poured steps are a stack of blocks: the first step is one riser tall, the second two, and so on, each one tread deep. Add the heights up — steps × (steps + 1) ÷ 2 risers — and multiply by the tread and the width. A flight of 5 steps at a 7-inch riser and an 11-inch tread, 3 feet wide, is about 24.1 cubic feet (0.89 yd³, 0.68 m³); in metric, 5 steps at a 180 mm riser and a 280 mm tread, 0.9 m wide, is about 0.68 m³ — enter your own figures above and the yardage and bag count appear instantly.
- Why not just half of rise × run?
- Because that smooth triangle runs from the bottom nosing to the top one and shaves the square nose off every step. It comes up short by one step in every (steps + 1) — about 17% on a five-step flight, 25% on three — and short is the wrong way to be mid-pour. This tool counts the true stepped shape.
- What if the stairs sit on a supporting slab or wall?
- Then work that part out separately. This tool covers the solid steps themselves. A throat slab beneath it, a landing at the top, or side cheeks are each their own rectangular pour — the slab and footing tools handle those, and you add the volumes together.
- How many bags will a short flight take?
- The bag count sits beside the volume, using a yield you can edit. Small exterior flights are firmly bag territory — a few steps rarely justify a truck and its minimum charge. Once the flight is wide, tall, or one of several, price a ready-mix delivery against the bag tally the tool gives you.
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