Per unit
The stepped cross-section is 3 blocks of 7 × 11 in (1 + 2), 1.6 ft² in all, so each extra foot of width adds 1.6 ft³.
Change the dimensions in the steps calculator. Why every count rounds up: how many bags of concrete you need.
Steps
Concrete for 2 solid steps, 3 ft wide
A solid poured staircase of 2 steps, 3 ft wide, with 7 in rises and 11 in treads. The volume is the stacked step cross-section times the width. That is 4.81 cubic feet, or 0.18 cubic yards: 9 bags of 80 lb premix or 11 bags of 60 lb, before any waste.
Concrete needed
0.18cubic yards· 0.136 m³· 4.81 ft³
| Bag size | Bags needed |
|---|---|
| 40 lb | 17 |
| 60 lb | 11 |
| 80 lb | 9 |
| 25 kg | 12 |
| 30 kg | 10 |
Planning estimate, with no waste allowance included. Add 5-10% for spillage and over-excavation, and check the yield printed on your bag. Structural work must follow your local building code and an engineer's specification.
Bagged or ready-mix?
Bags
0.18 yd³ is under a ready-mix supplier's usual one-yard minimum, so bags are the answer whatever the price per yard says. Buy a couple more than the count above and return what you do not open.
Same job, other sizes
Steps 3 ft wide
At this size
What changes on 2 solid steps, 3 ft wide
Mixing or ordering it
9 × 80 lb bags is 0.18 yd³ - a wheelbarrow-and-shovel job. Mix two bags at a time, keep the water tight to the bag's own figure, and place it in one go so there is no cold joint. No mixer, no delivery, no minimum load.
The dimensions used
| Steps | 2 |
|---|---|
| Rise | 7 in |
| Run | 11 in |
| Width | 3 ft |
How it is worked out
A solid poured staircase is a stack of rectangular blocks: the cross-section area is rise × run × n(n+1)/2 for n steps, and the volume is that area times the stair width. Seven-inch rises with eleven-inch runs are a comfortable, code-typical stair.
That volume - 4.81 ft³ - is divided by 27 to give 0.18 cubic yards, and by each bag's yield to give the bag count. An 80 lb bag of premix yields about 0.60 cubic feet, so this job takes 9 of them; bag counts always round up, because you cannot buy part of a bag.
Ordering ready-mix instead? Suppliers sell by the cubic yard (or cubic metre) and usually have a minimum load and a short-load surcharge - worth a call before you choose between bags and a truck.
Formwork
What is being measured
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