Curb
A 50 ft run of curb-and-gutter: a 6 in × 18 in curb with a 12 in × 4 in gutter pan. Both cross-sections are added before multiplying by the run.
Concrete needed
| Bag size | Bags needed |
|---|---|
| 40 lb | 181 |
| 60 lb | 121 |
| 80 lb | 91 |
| 25 kg | 132 |
| 30 kg | 110 |
At this size
91 × 80 lb bags is 2.01 yd³ - about 46 mixer batches. At this size the bag count is a costing reference rather than a plan: mixing 91 bags on site cannot keep ahead of the setting edge, so the pour ends up full of cold joints. Ordered by the yard it is part of a single load. Have the crew, the access and the discharge points sorted before anything arrives.
| Run | 50 ft |
|---|---|
| Curb | 6×18 in |
| Gutter | 12×4 in |
A curb is a long prism: its cross-section (width × height) times the run. For curb-and-gutter, the flat gutter pan (width × thickness) is added to the cross-section before multiplying by the length.
That volume - 54.17 ft³ - is divided by 27 to give 2.01 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 91 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
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