Per unit
Each foot of this plain curb holds 0.75 ft³, so one cubic yard pours about 36 ft of it.
One 80 lb bag fills about 10 in of run.
Change the dimensions in the curb calculator. Why every count rounds up: how many bags of concrete you need.
Curb
Concrete for a 100 ft curb
A 100 ft run of plain curb, 6 in wide and 18 in tall. The volume is the curb cross-section times the run. That is 75 cubic feet, or 2.78 cubic yards: 125 bags of 80 lb premix or 167 bags of 60 lb, before any waste.
Concrete needed
2.78cubic yards· 2.124 m³· 75 ft³
| Bag size | Bags needed |
|---|---|
| 40 lb | 250 |
| 60 lb | 167 |
| 80 lb | 125 |
| 25 kg | 182 |
| 30 kg | 152 |
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?
Either - check the short-load fee
2.78 yd³ clears the usual one-yard minimum but sits in the short-load band, where most suppliers add a surcharge for anything under about 3-4 yd³. That fee is what decides it: get it quoted, add it to the yard price, and compare against the bag count above at your own bag price.
Same job, other sizes
Plain curb
At this size
What changes on a 100 ft curb
Mixing or ordering it
125 × 80 lb bags is 2.78 yd³ - about 63 mixer batches. At this size the bag count is a costing reference rather than a plan: mixing 125 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.
The dimensions used
| Run | 100 ft |
|---|---|
| Curb width | 6 in |
| Curb height | 18 in |
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 - 75 ft³ - is divided by 27 to give 2.78 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 125 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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