Calculate the volume of concrete and number of bags needed to pour a flight of concrete steps from the rise, run and width.
Enter the number of steps, the rise (height of each step), the run (depth of each tread), the width and a waste allowance. A solid flight of concrete steps forms a staircase-shaped wedge, so the volume is more than a plain box — each step sits on the full block below it.
| Part | US | Metric |
|---|---|---|
| Rise (height) | 6–7.5 in | 150–190 mm |
| Run (tread depth) | 10–11 in | 250–280 mm |
Four steps, each 7 in rise × 11 in run, 4 ft wide. The staircase cross-section area is worked out step by step, then multiplied by the width. That comes to roughly 15 ft³ ≈ 0.55 yd³ of concrete. Add 10% waste ≈ 0.6 yd³.
Tip: you can save concrete on tall flights by filling the core with compacted hardcore (rubble) and only casting a 4–6 in concrete shell over the top.
It depends on the number of steps and their size. The calculator treats the flight as a solid staircase shape and works out the volume, bags and weight for you.
Around 150 to 180mm rise and 280 to 300mm run (going) is comfortable for outdoor steps. Keep every step the same size for safety.
Yes. Steps should sit on compacted hardcore and often a footing at the base to prevent settlement and cracking.
The calculator divides the total volume by the yield of a 25kg bag (about 0.0166 m³) and rounds up, but ready-mix is usually better for larger flights.
Yes, a 5 to 10 percent allowance covers spillage, over-dig and slightly oversized formwork so you do not run short mid-pour.
