Curb
A 50 ft run of plain curb, 6 in wide and 18 in tall. The volume is the curb cross-section times the run.
Concrete needed
| Bag size | Bags needed |
|---|---|
| 40 lb | 125 |
| 60 lb | 84 |
| 80 lb | 63 |
| 25 kg | 91 |
| 30 kg | 76 |
At this size
63 × 80 lb bags is 1.39 yd³ and roughly 32 mixer batches. This is the crossover point: bagging it is a full day with a mixer and at least two people, and the concrete has to keep arriving faster than the placed edge stiffens. Price 1.39 yd³ of ready-mix, short-load surcharge included, against 63 bags at your own bag price before you commit to a day of mixing.
| Run | 50 ft |
|---|---|
| Curb width | 6 in |
| Curb height | 18 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 - 37.5 ft³ - is divided by 27 to give 1.39 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 63 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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