Concrete Curb Calculator
A concrete curb calculator multiplies run × width × height (in ft) ÷ 27 for cubic yards: 50 ft of 6 × 6 in curb needs 0.46 yd³, or 0.51 yd³ with 10% extra.
How much concrete does a curb need?
This concrete curb calculator treats a curb as a long rectangular bar: cubic yards = length × width × (height in inches ÷ 12) ÷ 27. A 50 ft landscape curb that is 6 inches wide and 6 inches tall holds 0.46 cubic yards, or 0.51 cubic yards with the 10% waste box ticked. At $150 per yard, that is $69.44, or $76.39 with waste.
Enter the run length in feet, the curb width in feet, the curb height in inches, and your ready-mix price per cubic yard.
The formula in plain words
- Height in feet = height in inches ÷ 12.
- Cubic feet = run length × width × height in feet.
- Cubic yards = cubic feet ÷ 27.
- With waste = cubic yards × 1.10.
- Cost = cubic yards × price per yard.
Width is in feet because curbs are narrow. Convert inches to feet by dividing by 12: 4 in = 0.33 ft, 6 in = 0.5 ft, 8 in = 0.67 ft.
Worked examples
- Default landscape curb: 50 ft × 0.5 ft × 6 in, $150/yd³
- Cubic feet: 50 × 0.5 × 0.5 = 12.5 ft³
- Cubic yards: 12.5 ÷ 27 = 0.46 yd³, costing $69.44
- With 10% waste: 0.51 yd³, costing $76.39
- Driveway curb: 120 ft × 0.5 ft × 18 in, $150/yd³
- Height: 18 ÷ 12 = 1.5 ft
- Cubic feet: 120 × 0.5 × 1.5 = 90 ft³
- Cubic yards: 90 ÷ 27 = 3.33 yd³, costing $500.00
- With 10% waste: 3.67 yd³, costing $550.00
Ask the ready-mix plant about short-load fees. Many charge extra for small loads, which can change the math on a 3 to 4 yard order.
Concrete per 10 ft of curb
| Curb size (width × height) | Cubic feet per 10 ft | Cubic yards per 10 ft | 80 lb bags per 10 ft |
|---|---|---|---|
| 4 × 4 in | 1.11 | 0.041 | 2 |
| 6 × 6 in | 2.50 | 0.093 | 5 |
| 6 × 12 in | 5.00 | 0.185 | 9 |
| 6 × 18 in | 7.50 | 0.278 | 13 |
| 8 × 18 in | 10.00 | 0.370 | 17 |
Bags assume about 0.6 cubic feet per 80 lb bag, rounded up, without waste.
Curb vs curb and gutter
A plain curb is a single rectangle. A street-style curb and gutter adds a flat gutter pan in front, usually 18 to 24 inches wide, which can more than double the concrete per foot. For that shape, use the curb and gutter calculator.
How to measure your curb
- Run length: walk the line with a measuring wheel. Add every straight and curved section together.
- Width: the thickness of the curb from face to back. For a sloped face, use the average of top and bottom widths.
- Height: from the bottom of the trench to the top of the finished curb, not just the part showing.
- Driveway openings: subtract the length of any drop-curb section, then figure it separately at its lower height.
Common mistakes
- Entering width in inches. The width field is in feet. Typing 6 for a 6 in curb gives an answer 12 times too large.
- Measuring only the reveal. The buried part of a curb holds most of the concrete.
- Skipping expansion and control joints. Long curbs crack without them. Cut or tool joints at regular intervals per your local spec.
- Pouring onto loose soil. Compact the trench bottom or add a thin layer of base stone first.
Related calculators
Pouring a walkway next to the curb? Use the concrete sidewalk calculator. For a bag-mix pour, the concrete bag calculator counts 60 and 80 lb bags. For reinforcement, the rebar calculator totals bar length.
Frequently asked questions
What do the fields mean for a curb?
Length is the total curb run in feet, width is the curb's thickness in feet (6 inches is 0.5 ft), and depth is the curb's full height in inches, including any part buried below grade. The calculator treats the curb as a plain rectangle, which slightly overestimates a curb with a rounded or sloped top.
How many bags of concrete for a 50 ft landscape curb?
A 50 ft curb 6 inches wide and 6 inches tall is 12.5 cubic feet, or 0.46 cubic yards. One 80 lb bag yields about 0.6 cubic feet, so 12.5 ÷ 0.6 = 20.8, rounded up to 21 bags, or 23 bags with 10% extra. Ready-mix is usually easier once you pass about one cubic yard.
What's the difference between formed and extruded curbing?
Formed curbing is poured into wood or steel forms, so its section is a true rectangle and this calculator applies directly. Extruded or slip-formed curbing is pushed through a machine that shapes a profile with a sloped or rounded top, so it uses somewhat less concrete than the rectangle estimate.
How big should a curb be?
Decorative landscape edging is often 4 to 6 inches wide and 4 to 6 inches tall. Driveway and parking curbs are commonly 6 inches wide and around 18 inches tall, with roughly 6 inches showing above the pavement. Street curbs follow the local public-works standard drawing, so check local code before you form them.
Do I need rebar in a curb?
Small landscape curbs usually are not reinforced. Driveway, parking, and street curbs often get one or two continuous bars, and municipal curbs follow the city's standard detail. This calculator estimates concrete volume only.
Should I add extra concrete for a curb pour?
Yes. Tick the 10% box. Long narrow forms bulge, trenches get over-dug, and running short partway along a continuous run leaves a cold joint that is hard to hide. On a 120 ft driveway curb, 10% turns 3.33 yd³ into 3.67 yd³.
Estimates only. Verify quantities with your supplier before purchasing.