Concrete Stairs Calculator
Concrete for a flight of steps, treated as stacked rectangles rather than as a wedge, because stacked rectangles is how the forms are actually built.
Steps are computed as stacked rectangles rather than as a wedge. A wedge is the triangle they sit inside, which is about 50% of the true volume, so treating a flight that way orders half the concrete it needs — a mistake that surfaces with the truck already on site.
With number of steps 4, rise per step 7.5 inch, tread depth 11 inch, stair width 4 ft and 2 more fields, concrete comes to 0.93 cu yd — concrete needed. It is reached in 8 steps, the last of which is 25.208333 / 27, and each one is printed on the page with its numbers filled in. The formula is the one published by American Concrete Institute, not an approximation fitted to it.
Formula and sources checked · How we check
- Volume
22.917 cu ft- Volume with waste
22.916667 * (1 + 10 / 100)25.208 cu ft- Concrete needed
25.208333 / 270.934 cu yd- Cubic meters
0.933642 * 0.76455490.714 m3- 60 lb bags (0.45 cu ft each)
ceil(25.208333 / 0.45)57 bags- 80 lb bags (0.60 cu ft each)
ceil(25.208333 / 0.6)43 bags- Weight of the pour
0.933642 * 40503,781.25 lbs- Ready-mix cost at that price
0.933642 * 145135.378
Several at once
A job is rarely one of anything. Work out the first, add it, change the figures and add the next — the list keeps what each line was, and totals them.
Does the top landing count?
No. The top step of a flight is the landing it arrives at, and that slab is either poured separately or already there. Counting it adds a full step to the order: on a 4 ft wide flight, close to a fifth of a yard for concrete that has nowhere to go.
What about the sides of the flight?
A free-standing flight needs cheek walls, and those are a wall pour rather than a step pour. The figure above is the stepped volume between the forms and nothing else. Where both sides are open, price them as walls and add the two figures together.
The formula
- Volume
shape_slab * (length * width * thickness / 12) + shape_circle * (pi * pow(diameter / 2, 2) * thickness / 12) + shape_footing * (footing_length * footing_width * depth / 12) + shape_column * (pi * pow(hole_diameter / 2, 2) * height) + shape_wall * (wall_length * wall_height * wall_thickness / 12) + shape_stairs * (stair_width * rise / 12 * run / 12 * steps_count * (steps_count + 1) / 2) - Volume with waste
cubic_ft * (1 + waste / 100) - Concrete needed
cubic_ft_waste / 27 - Cubic meters
cubic_yards * 0.764554857984 - 60 lb bags (0.45 cu ft each)
ceil(cubic_ft_waste / 0.45) - 80 lb bags (0.60 cu ft each)
ceil(cubic_ft_waste / 0.60) - Weight of the pour
cubic_yards * 4050 - Ready-mix cost at that price
cubic_yards * price
Formula from American Concrete Institute, Portland Cement Association.
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