How much concrete for a 20 ft curb?
A 20 ft curb at 6 in wide × 12 in high is 10 cubic feet, or 0.37 cubic yards, before waste. Add 10% for about 0.41 cubic yards.
Curb calculator
Concrete Curb Calculator
Work out the concrete volume for a curb, curb-and-gutter run or garden edging. Enter the length, curb width and height; the calculator handles the unit conversion and bag counts.
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How to calculate concrete for a curb
Curb volume = length × curb width × curb height. Convert width and height to feet first, then divide cubic feet by 27 for cubic yards.
Example: 20 ft curb, 6 in wide × 12 in high
20 × 0.5 × 1 = 10 cubic feet. Divide by 27 to get 0.37 cubic yards. Add 10% waste for about 0.41 cubic yards, or roughly 20 × 80 lb bags.
Common curb runs at 6 in wide × 12 in high
| Size | Concrete | 80 lb bags* |
|---|---|---|
| 10 ft | 0.19 cu yd | 9 |
| 20 ft | 0.37 cu yd | 18 |
| 50 ft | 0.93 cu yd | 44 |
| 100 ft | 1.85 cu yd | 87 |
*Before waste. Add 5–10% for spillage and uneven subgrade.
Tips for ordering concrete for a curb
- Add 5–10% waste for spillage, uneven subgrade and rounded curb profiles.
- Confirm the curb width and height against the local standard or your project plan.
- Long runs are usually poured with ready-mix; bagged mix suits short garden curbs.
- Use the rebar toggle for longitudinal bars; the calculator spaces them across the curb width.
Concrete Curb Calculator FAQ
How wide and tall is a standard curb?
A common residential curb is about 6 in wide and 12 in high, but local standards vary. Measure the form or check the project plan before ordering concrete.
How many bags of concrete for a curb?
A 20 ft curb at 6 in × 12 in needs about 18 × 80 lb bags before waste, or roughly 20 bags with 10% waste. Longer runs are usually cheaper with ready-mix.
Does a concrete curb need rebar?
Long or structural curbs often use longitudinal rebar. Short garden curbs may not need reinforcement, but the requirement depends on the design and local standards.
How do I calculate curb and gutter concrete?
Calculate the curb and the gutter as separate rectangular volumes, then add them together. The calculator handles a simple rectangular curb; for a combined curb-and-gutter profile, ask your supplier to check the total.
How much does a concrete curb cost?
At $120–$180 per cubic yard, 0.41 cubic yards of ready-mix costs about $50–$75 before delivery. Small jobs may have minimum charges, so bagged mix can be cheaper for a short curb.
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