Kerb & Channel Concrete Volume Calculator
Estimate the concrete volume for kerb and channel (kerb and gutter) from the cross-sectional area and run length. Enter the profile area straight from the standard drawing, or let the calculator build a rough area from the kerb and channel dimensions, then add a waste allowance to get an order quantity.
Enter Values
Before you rely on this: First-pass guide only. Verify safety-critical or regulated work against the relevant standards, your project requirements and a qualified professional.
How to use this calculator
- Enter the kerb run length L in metres.
- Enter the cross-section area A (m²) if you have it from the standard profile — this overrides the dimensions.
- Otherwise enter the kerb height and width, and (for kerb-and-channel) the channel width and thickness in millimetres.
- Set a waste allowance (default 5%) and read the concrete volume, area used, volume per 10 m and barrow loads.
How it works
Concrete for a linear element equals its cross-sectional area times its length. If you supply the area A directly it is used as-is. Otherwise the tool approximates the section as a rectangular kerb (height h × width w) plus a rectangular channel slab (channel width cw × channel thickness ct), summing the two and dividing by 1,000,000 to convert square millimetres to square metres: A = (h·w + cw·ct) / 1e6. The net volume is A × L; the order volume adds waste as volume × (1 + waste/100). It also reports the volume per 10 m run and the number of 0.2 m³ wheelbarrow loads.
Worked example
Worked example. A 50 m kerb-and-channel with a 300 mm × 150 mm kerb and a 300 mm × 150 mm channel gives A = (300×150 + 300×150) / 1,000,000 = 0.09 m². Net concrete = 0.09 × 50 = 4.5 m³; with 5% waste = 4.725 m³ to order — about 23.6 barrow loads at 0.2 m³ each.
Common mistakes
- Using the rough rectangular estimate for a real profile. Barrier, mountable and semi-mountable kerbs have chamfers and curves, so their true area differs — use the exact area from the standard drawing when it matters.
- Mixing units: heights, widths and thicknesses here are in millimetres and the length is in metres. Entering the section dimensions in metres will make the area 1,000,000 times too large.
- Forgetting a waste/spillage allowance. Concrete is ordered in whole or half cubic metres, and some is always lost to spillage and over-excavation, so order a little above the net volume.
Frequently asked questions
Do I need the exact kerb profile area?
For accurate ordering, yes — take the cross-sectional area from your road authority's standard kerb drawing and enter it in the area field. The height/width/channel inputs are only a rough rectangular approximation for a quick estimate and will not match a chamfered or curved profile exactly.
How much waste should I allow for kerb concrete?
A 5–10% allowance is common to cover spillage, over-excavation of the bedding, and rounding up to the supplier's delivery increment. The default here is 5%; increase it for tight or awkward pours where more is likely to be lost.
How many wheelbarrows is a cubic metre of concrete?
A standard builder's barrow holds about 0.2 m³ when reasonably full (some are rated to 0.1 m³), so a cubic metre is roughly 5–10 barrow loads. This tool assumes 0.2 m³ per barrow; adjust your own count if your barrows are smaller.
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