What is the Concrete Stairs Calculator?
This calculator estimates how much concrete you need to pour a flight of stairs, including an optional top landing platform. It is built for any unit system that uses meters and works for residential entry steps, garden stairs, basement access steps and small commercial flights. The result is reported in cubic meters and cubic yards, along with an approximate weight and a rough premix-bag count so you can plan ordering and budgeting.
How to use it
Enter the number of steps, the rise (vertical height of each step), the run (horizontal depth of each step tread) and the stair width. If you are casting a landing at the top, add its depth and slab thickness; leave the platform depth at 0 if there is no landing. Click calculate to see the total volume.
The formula explained
A staircase fills a wedge-shaped (triangular) cross-section when viewed from the side. Each step adds a triangular prism whose cross-sectional area equals half of rise × run, multiplied by the stair width:
$$V_{\text{steps}} = n \times (0.5 \times \text{rise} \times \text{run} \times \text{width})$$
The optional top platform is a rectangular slab: \(\text{depth} \times \text{thickness} \times \text{width}\). The two are summed for the total. Note this triangular model is the standard approximation; it slightly underestimates a stair poured against a solid backing wall, so adding 5–10% waste is wise.
Worked example
For 5 steps with rise 0.18 m, run 0.28 m and width 1.0 m and no platform: each step = $$0.5 \times 0.18 \times 0.28 \times 1.0 = 0.0252 \text{ m}^3.$$ Five steps = 0.126 m³ of concrete — roughly 0.165 cubic yards and about 302 kg.
FAQ
Should I order extra concrete? Yes — add about 10% for spillage, over-excavation and uneven formwork.
What weight density is used? A standard 2400 kg/m³ for normal reinforced concrete.
How many bags do I need? The estimate assumes each 40 kg premix bag yields about 0.018 m³; large pours are far cheaper with ready-mix delivery.
