How do you calculate concrete for stairs?
Treat the staircase as a series of rectangles: compute each step's volume (width × tread depth × cumulative height) and add them, then divide by 27. Three 4-ft-wide steps with 7-inch rises and 11-inch treads total about 0.30 yards — roughly 14 bags of 80-lb mix.
Worked example: 3-step stoop, 4 ft wide, 7 in rise, 11 in tread
| Step | Height at that step | Volume |
|---|---|---|
| Step 1 (bottom) | 7 in | 4 × 0.917 × 0.583 = 2.14 ft³ |
| Step 2 | 14 in | 4 × 0.917 × 1.167 = 4.28 ft³ |
| Step 3 (top) | 21 in | 4 × 0.917 × 1.75 = 6.42 ft³ |
| Total | 12.83 ft³ | ÷ 27 = 0.48 yd³ solid-cast |
How to read this table
- Step 3 (top) sits at the top of the table (21 in) — 4 × 0.917 × 1.75 = 6.42 ft³. If your situation looks like this row, plan against the upper half of the range rather than the midpoint.
- Step 1 (bottom) anchors the bottom (7 in) — 4 × 0.917 × 0.583 = 2.14 ft³. Treat this as the conservative case you should still be profitable at.
- The gap between the top and bottom row is roughly 3.0×. That spread is why a single blended average is close to useless here — pick the row that matches your setup instead of averaging the column.
- With 4 reference points in the "worked example: 3-step stoop, 4 ft wide, 7 in rise, 11 in tread" table, the fastest way to use this page is to find the closest row, take its height at that step, then stress-test it ±30% before you build a plan on it.
Context
Most residential stoops are poured solid (as computed above) because the forms are simpler than building a hollow structure; large commercial stairs use a sloped slab with formed risers, which uses roughly half the concrete. Code sets the geometry: 7–7¾ inch maximum rise, 11-inch minimum tread, and consistent dimensions across the flight — a ¼-inch variation between steps is a trip hazard and an inspection failure.
What moves this number
Regional pricing
Ready-mix, bag, and labor prices vary 30–50% between US metros. Sun Belt markets with many plants run well below Northeast and remote-area pricing.
Waste and site conditions
Uneven subgrade, spillage, and form bowing consume 5–15% extra material. Orders placed at exact volume routinely come up short mid-pour.
Local code requirements
Frost depth, footing dimensions, and reinforcement rules are set by county. The same project can require twice the concrete in a northern climate versus a southern one.
Methodology
Solid-cast volume computed as the sum of step rectangles. Dimensions follow IRC R311.7 (max 7¾-in rise, min 10-in tread with nosing, ≤3/8-in variation). The hollow alternative is shown for comparison only.
Assumptions and caveats
- Volumes are theoretical; order quantities include a waste allowance but site conditions vary.
- Prices reflect 2026 US national ranges — get local quotes before budgeting a real pour.
- Structural dimensions and frost depths are governed by local building code; verify with your building department.
- This page was last reviewed on 2026-10-01. Ranges are updated as new data lands, so re-check before using them in a contract or a plan.
- Use these numbers as a starting range, not a guarantee — your own historical data always beats a benchmark.
Frequently asked questions
How do you calculate concrete for stairs?
Treat the staircase as a series of rectangles: compute each step's volume (width × tread depth × cumulative height) and add them, then divide by 27. Three 4-ft-wide steps with 7-inch rises and 11-inch treads total about 0.30 yards — roughly 14 bags of 80-lb mix.
Which option pays the most in the worked example: 3-step stoop, 4 ft wide, 7 in rise, 11 in tread table?
Step 3 (top), at 21 in (4 × 0.917 × 1.75 = 6.42 ft³). That row represents the strongest case in this dataset, so use it as an upper bound rather than an expectation.
What is a realistic low-end figure?
Step 1 (bottom) at 7 in (4 × 0.917 × 0.583 = 2.14 ft³). Plan your costs so the low end still works, then treat anything above it as upside.
Why do the numbers vary so much?
The spread between the highest and lowest row is about 3.0×. Regional pricing and waste and site conditions explain most of that gap — see the drivers section above for the full list.
Where do these numbers come from?
Solid-cast volume computed as the sum of step rectangles. Dimensions follow IRC R311.7 (max 7¾-in rise, min 10-in tread with nosing, ≤3/8-in variation). The hollow alternative is shown for comparison only.
How can I estimate my own number instead of using a benchmark?
Use the Concrete Cost Calculator on RevenueLab — it takes your own inputs and returns a figure specific to your setup, which is always more accurate than a published range.
Model your own numbers
Related reading
More answers in this category
- How do you calculate cubic yards of concrete?
- How many bags of concrete make a cubic yard?
- How do you calculate concrete for a slab?
- How do you calculate concrete for a driveway?
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Last updated 2026-10-01.