Formula and input notes
Solid stair volume = width × tread × rise × [step count × (step count + 1) ÷ 2]
| Input | Practical note |
|---|---|
| Tread depth | This is the horizontal depth assigned to each tread in the run calculation; confirm how nosing is treated in the governing layout convention. |
Worked concrete stairs example
Concrete Stairs Calculator example: For 7 solid steps, the stack factor is 7 × 8 ÷ 2 = 28.0. Multiplying by 45.9-in width, 12-in tread, and 6.69-in rise gives 2.43 yd³ after 10% allowance.
Read the concrete volume, bags, and material cost
Use the yardage only if the stair is genuinely solid or the chosen geometry matches the intended pour; otherwise model each component separately.
Forms, reinforcement, support, and stair-code checks
Landings, voids, sloped waist slabs, nosings, supports, reinforcement, forms, and irregular bottom or top steps can change concrete volume substantially.
Questions specific to this calculation
What concrete stair shape does the formula model?
It stacks equal solid rectangular step prisms. With n steps, the tread-by-rise cross-section contains n(n+1)/2 equal rectangles, which is multiplied by stair width.
When will the solid-step estimate overstate concrete?
A suspended stair slab, hollow form, fill-supported stair, landing, sloped waist, nosing profile, or separate foundation does not match the solid staircase model. Break those components into their actual shapes.
Does this tool design the stair or reinforcement?
No. It does not check stair-code geometry, loads, reinforcement, cover, support, foundations, joints, finishing, or form pressure.