Concrete Stairs Calculator
Enter the total rise and width of your steps to get the exact number of bags, riser/tread layout, and a code check for your stairs.
Your stairs
Bottom landing to top landing, vertically.
7 in is the common comfortable target.
Fills in from total rise ÷ target riser if left blank.
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Bags or ready-mix?
Bags make sense here
Mixing time
5 h 18 m
One person, 53 bags
Water & weight
39.8 gal
Water needed for the full mix
The short answer
Concrete stairs are stacked steps, so each one carries the full height of every step beneath it. Volume in cubic feet works out to width × tread × riser × the sum of 1 through the number of steps. Four typical 36 in wide steps, 7 in risers and 11 in treads, come to roughly 16 cu ft — about 27 bags of 80 lb mix before waste. Add 5–10% waste and always round up.
Concrete needed per step count
Reference figures for a common 36 in wide flight with 7 in risers and 11 in treads, before waste. Volume climbs quickly because every added step also carries the height of every step below it.
| Steps | Total rise | Cubic feet | 80 lb bags |
|---|---|---|---|
| 1 | 7 in | 1.6 | 3 |
| 2 | 14 in | 4.8 | 9 |
| 3 | 21 in | 9.6 | 17 |
| 4 | 28 in | 16.0 | 27 |
| 5 | 35 in | 24.1 | 41 |
| 6 | 42 in | 33.7 | 57 |
| 8 | 56 in | 57.8 | 97 |
| 10 | 70 in | 88.2 | 148 |
Riser and tread code minimums
These are common residential targets, not a substitute for your local building code — always confirm with your building department before pouring.
| Measurement | Typical minimum / maximum | Comfortable target |
|---|---|---|
| Riser height | 4 in min · 7.75 in max | 7 in |
| Tread depth | 10 in min | 11 in |
| Riser variance in one flight | 3/8 in max between steps | 0 in |
| Comfort formula | 2 × riser + tread | 24–25 in |
How to calculate concrete for stairs
Stairs are not a simple box — each step is a slab stacked on the ones before it, so the formula sums the height carried by every step.
- Find the total rise. Measure vertically from the bottom landing to the top landing.
- Choose a riser height. Around 7 in is comfortable. Divide total rise by this to get the step count, then round to a whole number.
- Recalculate the actual riser. Total rise ÷ number of steps — this evens out the rounding across every step.
- Set the tread depth and width, then sum the stacked volume: width × tread × riser × n(n+1)/2.
- Add waste and round up to a whole number of bags, or convert to cubic yards for ready-mix.
Worked example
A 36 in (3 ft) wide entry stair with a 35 in total rise, 7 in risers and 11 in treads:
- Steps35 ÷ 7 = 5
- Stacked volume3 × 0.917 × 0.583 × 15 = 24.1 cu ft
- Plus 10% waste26.5 cu ft
- Divide by bag yield26.5 ÷ 0.60 = 44.2
- Round up45 × 80 lb bags
That’s a full pallet plus a handful of extra bags — worth pricing a small ready-mix load too if a supplier will deliver less than a yard.
Solid pour vs hollow core
This calculator assumes a solid pour from the ground up, which is standard for small residential flights of a few steps. Taller stairs are often built hollow — with block, foam, or compacted fill under the treads — to cut weight and material cost. That trims volume significantly but turns the job into a structural design rather than a simple calculation, so get an engineer or experienced contractor involved above roughly 4–5 steps or any structural loading.
Common mistakes
- Using average height instead of the stacked formulaMultiplying width × tread × total rise badly overestimates volume, since only the top step actually reaches the full height.
- Uneven risersEven a 3/8 in difference between steps is a tripping hazard and often fails inspection. Always divide total rise evenly across all steps.
- Skipping rebarUnreinforced steps crack along the riser lines within a few freeze-thaw cycles in most climates.
- No slope on treadsFlat treads pool water and ice over. A slight forward slope (about 1/8 in per foot) sheds water.
- Forgetting the landing padA top landing is a flat slab, not a step — add it separately, it doesn’t follow the stacked-step formula.
- Ordering the exact countRound up, then keep a spare bag or two on hand. Concrete waits for no one once it’s mixed.
What this calculator assumes
Adjust your result if your project differs from these.
- Solid concrete stairs poured on a compacted, undisturbed base — no hollow core
- Bag yields of 0.60, 0.45, 0.375 and 0.30 cu ft for 80, 60, 50 and 40 lb bags
- Standard concrete mix, not fast-setting or high-strength products
- Step count rounds to the nearest whole number, with rise then split evenly
- Water of roughly 3 quarts per 80 lb bag
- Mixing at about 6 minutes per 80 lb bag, per person
- Prices are whatever you enter; they are not live market rates
Common questions
How much concrete do I need for outdoor steps?
It depends on rise, tread, width and step count. Four typical 36 in wide steps with a 7 in riser and 11 in tread need roughly 16 cu ft, about 27 bags of 80 lb mix, before waste.
What is the standard rise and run for concrete steps?
Most residential codes allow a maximum riser around 7.75 in and a minimum tread of 10 in, with 7 in risers and 11 in treads the common comfortable target. Always confirm with your local code.
How many bags of concrete per step?
It rises with each step, since every step sits on top of the ones below it. For a 36 in wide, 7×11 in step, the first step alone needs about 3 bags — the fourth needs roughly 10 more on top of that, because it carries the full height beneath it.
Should concrete stairs be poured solid or hollow?
Small residential flights are usually poured solid. Taller stairs are often built hollow with block or fill under the treads to save material and weight, which needs a structural design rather than a simple volume calculation.
Do I need rebar in concrete steps?
Yes, for anything beyond a single low step. Rebar or mesh ties the steps to the footing and resists cracking from freeze-thaw and settlement. Check your local code for size and spacing.
Is it cheaper to buy bags or ready-mix for stairs?
Bags are usually cheaper and more practical below about half a cubic yard, which covers most single flights of stairs. Above that, price a small ready-mix load — but watch the short-load fee, which can erase the saving on small orders.
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materialcalculate.com/concrete-stairs-calculator/
Stair layout
| Total rise | — |
| Steps | — |
| Actual riser × tread | — |
| Width | — |
| Landing | — |
| Waste allowance | — |
Volume
| Cubic feet (incl. waste) | — |
| Cubic yards | — |
| Cubic metres | — |
Shopping list
| 80 lb bags | — |
| 60 lb bags | — |
| 40 lb bags | — |
| Water needed | — |
| Dry weight to move | — |
| Estimated cost | — |
Notes
Estimate generated by materialcalculate.com. Assumes a solid pour with bag yields of 0.60, 0.45, 0.375 and 0.30 cu ft for 80, 60, 50 and 40 lb bags. Confirm riser/tread limits with your local building code before pouring.