Concrete Stairs Calculator
Concrete for a solid flight of steps poured on the ground.
Your result
Enter your step dimensions above to see how much concrete you need.
Step dimensions are regulated. The rise and going have to fall within the ranges set by the National Construction Code, they must be consistent within a flight, and handrails and landings have their own requirements. This works out concrete, not compliance.
Why stairs use more concrete than people expect
The instinct is to treat a flight as a wedge — total rise times total run, halved, like a triangle. That under-orders, and it does so by more as the flight gets bigger.
A solid flight is not a triangle. Each step sits on concrete all the way to the ground, so side-on the profile is a staircase, not a slope. Every step contributes a rectangle, and the rectangles get taller as you go up:
Cross-section = going × rise × n(n + 1) ÷ 2
For three steps at 180 mm rise and 280 mm going, that is 0.28 × 0.18 × 6 = 0.3024 m². At a metre wide, 0.30 m³. The triangle method gives 0.23 m³ — about 25% short.
The gap widens with the flight. At six steps the triangle method is roughly 15% short; the error never disappears, because it is exactly half a step's volume per step.
Volume grows faster than step count
Because of the n(n + 1) ÷ 2 term, doubling the number of steps more than doubles the concrete. Three steps at the dimensions above need 0.30 m³; six need 1.06 m³, not 0.60 m³. It is worth checking the number before you order.
Rise and going
Rise is the vertical height from one tread to the next. Going is the horizontal depth of the tread you stand on. Both are measured per step, not for the whole flight.
Common domestic figures are around 170–190 mm rise and 250–300 mm going, but the permitted ranges, and the relationship between the two, are set by the National Construction Code. They are not a matter of preference, and a flight that is comfortable is not automatically a flight that complies.
One thing worth getting right before you pour: every step in a flight must be the same. An uneven step is both a trip hazard and a failure at inspection, and concrete is unforgiving about it.
If your steps are not solid
This calculator assumes a solid pour onto the ground. Two common cases need less concrete:
- Built over fill. Many garden steps are formed over compacted road base, with a concrete skin on top. Work out the fill volume separately and subtract it — the road base calculator will give you the loose quantity to order.
- Suspended or cantilevered flights. These are a slab with steps formed on top, not a solid mass, and the volume depends entirely on the engineer's detail. Use the drawing, not this.
Frequently asked questions
How do I include a landing at the top?
Work it out as a separate rectangular pour with the concrete calculator and add the two figures. A landing is just a slab; mixing it into the step count would distort the staircase formula.
Why is this more than the figure I calculated myself?
Almost certainly the triangle method — total rise × total run ÷ 2. That treats the flight as a ramp. A solid flight has a square corner at every step, and those corners add up to exactly half a step's volume per step.
Do I subtract the reinforcement?
No. Bar and mesh displace very little concrete relative to the pour, far less than the waste allowance covers.