How many feet of curb you get per yard of concrete depends on the curb's cross-sectional area. The math is simple, but the result varies significantly by curb type. A 6-by-12-inch barrier curb runs roughly 54 linear feet per yard at the section — but you have to add waste factor and account for the slipform machine's continuous-feed loss before you place the order.
What follows: the formula, common curb types, the logic behind the waste factor, and how to turn it all into a clean concrete-truck order.
What is the formula?
Direct answer: One cubic yard of concrete equals 27 cubic feet. Linear feet of curb per yard equals 27 divided by the curb's cross-sectional area in square feet. A 6-inch by 12-inch barrier curb (0.5 sq ft) yields 54 linear feet per yard at the section. After the standard 10 percent waste factor, plan to order one yard of concrete for every 49 linear feet of finished curb.
The base formula
Linear feet per cubic yard = 27 / (cross-section width in feet x cross-section height in feet)Where:
- 27 = cubic feet in one cubic yard
- Width and height are the curb's cross-section dimensions, converted to feet
For a 6-inch face by 12-inch base curb:
- Width = 12 inches = 1.0 ft
- Height = 6 inches = 0.5 ft
- Cross-section area = 1.0 x 0.5 = 0.5 sq ft
- Linear feet per yard = 27 / 0.5 = 54 lf
Common curb cross-sections and yields
| Curb Type | Cross-Section | Cross-Section Area | Linear Feet Per Yard (Section) |
|---|---|---|---|
| 4-inch face mountable curb (4x12) | 4 in x 12 in | 0.33 sq ft | ~82 lf |
| 6-inch face barrier curb (6x12) | 6 in x 12 in | 0.50 sq ft | ~54 lf |
| 6-inch face (6x18 base) | 6 in x 18 in | 0.75 sq ft | ~36 lf |
| 8-inch heavy-duty barrier curb (8x16) | 8 in x 16 in | 0.89 sq ft | ~30 lf |
| Ribbon curb (4x12) | 4 in x 12 in | 0.33 sq ft | ~82 lf |
| Curb and gutter (6-inch curb + 24-inch gutter) | 6 in x 30 in (combined) | 1.25 sq ft | ~22 lf |
| Granite curb (5x10 typical) | 5 in x 10 in | 0.35 sq ft | ~78 lf (but precast, not poured) |
Why you need a waste factor
A 10 percent waste factor on top of the section yield accounts for:
- End losses on each truck. The first and last 5 to 10 feet of each truck delivery typically have stiffer or wetter concrete than the target slump. Some gets discarded.
- Slipform machine reset. Each time the machine starts, stops, or transitions between sections, a small amount of concrete is wasted in the changeover.
- Form-board volume. Hand-formed pours always over-pour the forms slightly because the screed pulls excess off the top.
- Section variance. Subgrade isn't perfectly level. Low spots in the prepared base soak up extra concrete from the bottom of the section.
- Hand-finished features. ADA ramps, drive-aisle radius corners, and expansion-joint blockouts often need touch-up pours that draw from the main truck.
After the 10 percent waste factor:
| Curb Type | Theoretical lf/yd | After 10% Waste (Order Rate) |
|---|---|---|
| 4-inch mountable (4x12) | 82 lf | 74 lf per yard ordered |
| 6-inch barrier (6x12) | 54 lf | 49 lf per yard ordered |
| 6-inch barrier (6x18) | 36 lf | 33 lf per yard ordered |
| 8-inch heavy-duty (8x16) | 30 lf | 27 lf per yard ordered |
| Curb and gutter (6+24) | 22 lf | 20 lf per yard ordered |
How to calculate your concrete order
- Measure your total linear footage -- run the tape along the centerline of every curb section. Don't forget radius corners and ADA ramps.
- Pick the cross-section that matches your spec. The civil drawings will show it.
- Look up the order rate in the table above (or compute it: 27 / area / 1.10).
- Divide your total footage by the order rate to get cubic yards.
- Round up to the next half-yard. Truck plants typically deliver in half-yard increments.
Worked example: 740 lf of 6-inch barrier curb (6x12)
- Linear footage: 740 lf
- Order rate: 49 lf per yard ordered
- Yards needed: 740 / 49 = 15.1 yards
- Round up: 15.5 yards
Order 15.5 cubic yards of Class 4000 concrete from the supplier. That accounts for the 10 percent waste factor and gives you a comfortable buffer.
What if my curb has a non-rectangular cross-section?
Most modern parking-lot curbs use one of two non-rectangular shapes:
Mountable curb with sloped top
A 4-inch face mountable curb tapers from 4 inches at the back to roughly 1 inch at the front over a 12-inch base. The cross-section becomes a trapezoid. Use the average height (2.5 inches) times the base width (12 inches) for the area calculation: 0.21 sq ft yields 130 lf per yard at the section, or 118 lf per yard ordered after waste.
Curb and gutter monolithic section
A 6-inch face curb on top of a 24-inch gutter pan with a sloped pan profile. The cross-section is roughly L-shaped. Compute the curb portion (6x6 = 0.25 sq ft) and the gutter pan separately (typically 4-inch average depth x 24-inch width = 0.67 sq ft) and add them. Total 0.92 sq ft yields ~29 lf per yard at section, ~26 lf per yard ordered.
The supplier's mix-design ticket usually states the section area for the spec'd curb. If it does, use that number directly.
What about ADA curb ramps?
ADA ramps don't follow the linear-foot calculation -- they're priced and measured per ramp. A standard 36-inch wide by 4-foot long cast-in-place ramp at 6 inches average depth uses about 0.07 cubic yards of concrete per ramp. Add a 25 percent waste factor (ramps have more form-pour and transition loss than continuous slipform): order roughly 0.09 cubic yards per ramp.
For 4 ramps on a project: 0.09 x 4 = 0.36 yards. Round up to 0.5 yards on the order or include it in the main curb pour overage.
Ready to scope a concrete curb project?
We handle the yardage calculation, supplier ordering, slipform machine staging, and waste-factor management on every commercial parking-lot curb job. Contact Cojo for a site walk and a written scope — the quote includes the concrete order math broken out so you can sanity-check it.