Overview
What is the Concrete Stairs Calculator?
A stair calculator estimates the concrete in a straight flight with optional top landing depth. You provide unit run, unit rise, stair width, platform depth, and riser count. Building-code rise and run limits, nosings, and reinforcement are not selected here — only volume.
Stair volume is not a single rectangle. Enter tread run, riser height, width, platform depth, and how many risers you are pouring. The calculator uses the stair geometry already in the Calnovix engine, then adds waste so you can order enough concrete for the stringer pour without treating the flight like a slab.
Workflow
How does it work?
The engine converts run, rise, width, and platform to metres. Volume is width × rise × (platform × n + run × n × (n + 1) / 2), where n is the riser count. That matches the stair case in the shared concrete engine. Waste then scales the total.
Set Imperial or Metric so treads and risers match the drawing (often inches or millimetres).
Choose Stairs so the form asks for run, rise, width, platform, and risers.
Enter the unit tread run and unit riser height, not the total going of the flight.
Set stair width and any landing / platform depth included in the pour.
Enter the number of risers, add waste, then calculate.
Treat complex winders or curved stairs as a sketch take-off in addition to this straight-flight model.
Math
Formula
V = width × rise × (platform × n + run × n × (n+1) / 2)
Each riser adds a triangular-prism step that grows with the going of the flight, plus a rectangular landing if platform depth is set. n is the riser count. All lengths convert to metres first. Waste multiplies the raw volume. This is the same formula the main concrete calculator uses for the stairs shape.
Inputs
Step-by-step variables
run
Tread run
Horizontal depth of one tread (unit going), not the total stair length.
rise
Riser height
Vertical height of one riser. Codes often cap this dimension.
n
Risers
Number of risers in the flight you are pouring.
width
Stair width
Clear width of the pour between stringers or forms.
Practice
Step-by-step examples
Ten risers, 11 in run, 7 in rise, 4 ft wide
Straight flight, 12 in platform, 10% waste. Convert run and rise to feet, then apply the stair formula with n = 10 and width = 4 ft.
About 5.22 yd³ raw (≈ 141 ft³), or roughly 5.75 yd³ with 10% waste. Ready-mix is the usual order at this size.
Four-riser stoop, 10 in run, 7.5 in rise, 3 ft wide
A short stoop with a 16 in top platform, 8% waste. Fewer risers cut volume quickly compared with a full flight.
About 0.55 yd³ after waste. Bags can work if access for a truck is poor; confirm on the result card.
Where it helps
Use cases
- Straight exterior stairs against a porch or deck
- Basement or garage flights poured with a top landing
- Comparing a stoop volume with leftover slab concrete
Avoid these
Common mistakes
- Entering total stair length as the unit run, which overstates every tread.
- Counting treads instead of risers.
- Ignoring the landing when it is poured monolithically with the flight.
Buying & planning
Tips
- Confirm rise and run on the code drawing before you lock formwork.
- Brace the stringers; a stair pour is top-heavy compared with a slab.
- Order a little extra — stair forms are unforgiving if you run short on the last treads.
Need the bigger picture? Read our calculator disclaimer and accuracy policy.