The dimensions used
| Run | 100 ft |
|---|---|
| Curb | 6×18 in |
| Gutter | 12×4 in |
Curb
Concrete for a 100 ft curb and gutter
A 100 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
4.01cubic yards· 3.068 m³· 108.33 ft³
| Bag size | Bags needed |
|---|---|
| 40 lb | 362 |
| 60 lb | 241 |
| 80 lb | 181 |
| 25 kg | 263 |
| 30 kg | 219 |
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.
How it is worked out
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 — 108.33 ft³ — is divided by 27 to give 4.01 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 181 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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