Concrete Curb & Gutter Calculator: Volume for L-Shaped Curbing
This calculator handles the L-shaped cross-section of curb and gutter by combining the standing curb and the flat gutter flag into one volume. Enter curb height and depth, gutter width, flag thickness, and total length to get cubic yards and cost for your run.
Estimated concrete
Estimates only. Add ~5–10% for waste. Bag yields: 40 lb ≈ 0.30, 60 lb ≈ 0.45, 80 lb ≈ 0.60 cu ft. Concrete ≈ 150 lb per cu ft.
How to Use the Curb & Gutter Calculator
- 1
Enter your dimensions
Type the length, width and thickness of your slab, footing or pad and choose your units, feet, inches or meters.
- 2
Get instant volume
See the result in cubic yards, cubic feet and cubic meters, plus weight, the moment you type, no page reloads.
- 3
Buy the right amount
We convert volume into the exact number of 40, 60 and 80 lb bags, truck loads and cost so you order without waste or shortfalls.
The formula
cubic yards = [cross-section area (curb + gutter) in ft² × Length_ft] ÷ 27
- ·cross-section area = combined curb and gutter profile (ft²)
- ·curb portion = curb width_ft × curb height_ft
- ·gutter portion = gutter width_ft × gutter thickness_ft
- ·Length_ft = run of curb (ft)
- ·27 = cubic feet per cubic yard
Draw the L-shaped profile, split it into the vertical curb rectangle and the flat gutter pan, add their areas, then multiply by the run length. Convert every inch dimension to feet by dividing by 12.
Worked examples
Example 1: Standard 6 in curb + 18 in gutter, 100 ft run
- Curb = (6÷12) × (12÷12) = 0.5 × 1.0 = 0.5 ft²
- Gutter = (18÷12) × (6÷12) = 1.5 × 0.5 = 0.75 ft²
- Cross-section = 0.5 + 0.75 = 1.25 ft²
- Volume = 1.25 × 100 = 125 ft³ ÷ 27 = 4.63 yd³
Result: ≈4.63 cubic yards (about 5.1 yd³ with 10% waste)
Example 2: Lighter curb profile, 1.0 ft² section, 60 ft run
- Cross-section area = 1.0 ft²
- Volume = 1.0 × 60 = 60 ft³
- Yards = 60 ÷ 27 = 2.22 yd³
- +10% waste ≈ 2.44 yd³
Result: ≈2.22 cubic yards (order ~2.5 yd³)
Concrete calculators by project type
Concrete bag yield & coverage
How much mixed concrete a standard bag yields, and how far a cubic yard goes at common slab depths.
| Bag size | Yield (cu ft) | Bags per cubic yard |
|---|---|---|
| 40 lb | 0.30 | 90 |
| 60 lb | 0.45 | 60 |
| 80 lb | 0.60 | 45 |
- 40 lb
- 60 lb
- 80 lb
Related guides
Curb & Gutter Concrete FAQs
How do you calculate concrete for curb and gutter?
Break the L-shape into two rectangles: the vertical curb (height by depth) and the horizontal gutter flag (width by thickness), then multiply the combined cross-sectional area by the length. This calculator does that math and converts it to cubic yards for you.
What is a standard curb and gutter size?
A common combined curb and gutter is a 6-inch curb height with an 18- to 24-inch gutter pan and a 6-inch flag thickness. Municipal specs vary, so check your local standard detail before ordering.
How many cubic yards of concrete per foot of curb and gutter?
A typical 6-inch curb with a 24-inch gutter runs roughly 0.03 to 0.04 cubic yards per linear foot. That means about 100 feet of curb needs 3 to 4 yards of concrete.
What is the flag on a curb and gutter?
The flag is the flat, sloped gutter portion that carries water alongside the raised curb. Flag thickness is usually 6 inches and is measured separately from the curb height in this calculator.
What concrete mix is used for curb and gutter?
Curb and gutter is typically poured with a stiff, low-slump 3,000 to 4,000 psi mix so it holds its shape when machine-extruded or hand-formed. Ask your ready-mix supplier for a curb mix if you're slipforming.
Should I add extra concrete for curb and gutter?
Yes, order about 5 to 10% extra to cover subgrade variation, form deflection, and waste at the ends. Curb runs are unforgiving, so it's better to have a little surplus than to stop mid-pour.
How do you form curb and gutter by hand?
Set inner and outer form boards to the curb and gutter dimensions on a compacted base, then pour, screed the gutter pan, and shape the curb face and back with a curb tool. Radius points use flexible form material. Hand forming suits short runs; long stretches are usually slip-formed.
What slope should a gutter pan have?
The gutter pan is pitched toward its flow line, and the roadway drains toward the gutter at roughly 2%. Longitudinal fall along the curb typically follows the street grade, often a minimum of about 0.4% so water keeps moving. Slope does not change the concrete volume meaningfully.
How much does curb and gutter cost per linear foot?
Installed curb and gutter commonly runs about $15 to $35 per linear foot depending on region, profile, and site access. The concrete itself is only a fraction of that; forming, machine time, and finishing dominate. Use the volume estimate to price the ready-mix portion separately.
Can curb and gutter be poured with a slip-form machine?
Yes. A slip-form paver extrudes a continuous curb and gutter profile in one pass and is standard on larger jobs. It needs a stiff, low-slump mix and a well-prepared stringline for grade. The cross-section it produces is what you plug into the volume formula.
How thick is a typical gutter pan?
Gutter pans are commonly 6 inches thick, matching the adjacent pavement or slightly thicker at the flow line. Thickness feeds directly into the gutter portion of the cross-section area. Confirm your local standard detail, since municipal specs vary.
How far apart are control joints in curb and gutter?
Tooled or sawn contraction joints are usually spaced about every 10 to 15 feet, with expansion joints at longer intervals and at structures. Joints control where the curb cracks. They do not affect the total concrete quantity, only the finishing.
Do you need rebar in curb and gutter?
Many standard residential curbs use no continuous rebar and rely on joint spacing to manage cracking, though dowels are used at joints and some specs call for longitudinal bars. Structural or heavily loaded curbs may require reinforcement. Follow the local standard detail for your project.