Channel Drainage Calculator – Sections, Concrete & Cost
THE HANDYMAN HUB · FREE CALCULATOR
Channel Drainage Materials Calculator
Estimate channel sections, optional grates, fittings, concrete bedding, excavation and job costs.
YOUR ESTIMATE
Your channel drainage estimate
Run quantities, materials and optional job price.
Enter channel runs and section length, then calculate.
Inputs changed. Calculate again to update your estimate.
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Plan the channel run alongside paving and levels
Use this calculator for material quantities in a specified channel drainage layout: straight channel sections, fittings and optional concrete and excavation. Confirm the selected product and outlet arrangement before turning the purchase list into an order.
For the adjoining surface, the paving and patio calculator estimates its separate paving and base materials. The fall and gradient calculator converts a supplied fall into levels; it does not choose drainage capacity or an outlet. Keep the channel excavation separate from the patio excavation where their measured footprints differ.
A specified buried aggregate-and-pipe trench belongs in the French drain calculator. These tools cover different material schedules. If concrete bedding is already enabled in this channel estimate, do not add the same quantity again from the concrete calculator.
MEASURE · DRAIN · ESTIMATE
Channel drainage calculator for sections, concrete and costs
This free channel drainage materials calculator estimates straight channel sections across one or more runs. Add separately purchased grates, layout fittings, concrete bedding and haunching, trench excavation and optional job costs. The result shows how each run rounds to whole sections and how purchases account for pack sizes and existing stock.
The calculator estimates quantities from a specified system and measured layout. It does not size a drain for rainfall or choose its load class, discharge route, level or concrete installation detail. Establish those requirements first, then enter the dimensions and compatible products that apply.
How to use the calculator
- Select metres and millimetres or feet and inches.
- Add the straight channel length for each separate run.
- Enter effective installed length per channel section and sections per purchase pack.
- Add optional spare sections, whole stock and pack prices.
- Enable separate grates and fittings only where needed.
- Enter specified concrete and assessed trench dimensions if you want those quantities.
- Add optional labour and other costs, calculate, review and print.
Measure straight runs after allowing for fittings
Enter the length occupied by straight channel sections. If a separate corner, sump or other fitting occupies part of the route, allow for that fitting before entering the remaining straight run. The calculator does not know the dimensions of every fitting and does not automatically shorten the entered lengths.
Use a separate row for each straight run or section of the layout. Identical copies repeat the row’s length and rounding. A route that changes direction can be split into its straight parts, with compatible junctions entered in the optional fittings section.
Bulk entry accepts a name, straight length and copy count for each row. It produces the same result as the run cards. Keep names short and avoid commas within names when using comma-separated data.
Installed section length and whole purchases
Use the effective installed coverage of one channel section. A product’s overall physical or packaging length may include a connector that does not add to the installed run. Confirm the relevant dimension for the exact system rather than assuming all nominal one-metre products join identically.
Each run divides by the effective section length and rounds up to a whole section. Two separate 2.2 m runs made from 1 m sections each require three sections under this method, giving six in total. The tool does not assume that a cut offcut from one run can become a usable section in another.
The run breakdown shows the amount of the final section used and the remaining offcut. This is a numerical cutting allowance, not permission to cut at any position. Some systems have designated cutting points, locking details or outlet features that affect the usable arrangement.
After all run sections and copies are added, optional spare sections increase the requirement. The total then rounds to purchase packs, and complete matching packs already owned are deducted. The entered price is per purchase pack, not automatically per metre or per individual section.
Separate grates and layout fittings
Many channel products include their grate or cover. Leave the separate-grate option off when that is already included in the channel price. If grates are bought separately, enter the compatible coverage length and purchase pack size. Grates round independently for each straight run.
Fitting-specific covers are not inferred from straight runs. Check corners, access units, sumps and any special pieces against the supplier’s component list. Mixing a channel body with an incompatible grate can affect both installation and performance.
The fittings section allows explicit counts for end caps, outlet adaptors, corner units, T junctions, sump or access units and separate connectors. No fitting is automatically assumed at every end or on every run. A joined route may have a very different number of ends and outlets from a collection of independent runs.
The result reports straight internal joint count as a reference. Clip-together products may not require a separately purchased connector for each joint. For example, ACO describes HexDrain channels as clipping together. Follow the exact chosen system’s connection and sealing instructions when deciding what to purchase.
Concrete bedding and haunching quantities
The optional concrete estimate uses a simple constant rectangular section along the entered straight lengths. Enter the channel body’s outside width, the bed thickness below it, the concrete width on each side and the side concrete height above the bed.
The bed runs under the channel and both side strips. Its area is channel width plus twice the side width, multiplied by bed thickness. The two haunches add twice the side width multiplied by their height above the bed. Keeping that height above the bed prevents the same concrete from being counted twice.
Multiply the combined cross-sectional area by total straight length to obtain volume. Add separately assessed concrete for end details, fittings and pits, then apply the entered reserve. If the actual surround is sloping, irregular or varies along the route, split the estimate or use a separately assessed additional volume.
The calculator deliberately does not provide default concrete dimensions or strength. Those depend on the selected product, loading, surrounding construction and installation requirements. Polypipe’s channel drain guidance illustrates the importance of following the manufacturer’s installation recommendations for the intended use.
Volume only, bagged concrete or ready-mix
Volume-only mode reports concrete without adding a purchase price. Bagged mode requires the finished mixed yield per bag. Dry bag weight alone is not a usable volume, so do not treat a kilogram figure as litres.
Bagged concrete divides the required volume by finished yield, rounds up to whole bags and subtracts complete usable bags already available. Metric yield is entered in litres; imperial yield is entered in cubic feet. Use the current supplier information for the actual concrete product.
Ready-mix mode rounds required concrete up to the entered order increment. Metric volume and price are per cubic metre; imperial volume and price are per cubic yard. Delivery charges or minimum-load charges can be added to other whole-job costs if they are not already included.
Trench excavation and loose spoil
Excavation is a separate optional calculation using the total assessed trench width and depth along the straight runs. Add extra excavation volume for sumps, connections or pits. The total depth should already include the full excavation required; the calculator does not add the concrete bed depth again.
In-situ volume describes material before excavation. The bulking percentage increases that volume to estimate loose spoil. The calculator does not automatically deduct channel or concrete volume from spoil, because those are installed materials rather than material left unexcavated.
These dimensions are quantity inputs, not advice on safe trench size, support, working space or underground services. Disposal, transport and reinstatement can be assessed separately and included in other costs or the wider project estimate.
Labour and job pricing
Length-based labour uses entered straight channel lengths and copies, without spare sections or purchase rounding. Use a rate that covers the intended work or choose hours or days where preparation, connections and detailing dominate.
Other costs can include assessed sealant, pipe connections, fitting labour, waste removal, delivery and tools. Avoid adding items already included in a kit, channel pack or contractor rate. All prices start at zero and labour starts at None.
Turning an optional checkbox off excludes that section’s quantities and costs while retaining its entries. Closing a pricing details panel retains active values. Markup adds to total cost and the entered tax applies afterwards; markup is not the same as profit margin.
Frequently asked questions
Does this tell me which channel size I need?
No. Hydraulic capacity, load class, outlet route and suitable system details must be established separately.
Are grates included automatically?
The base estimate assumes you price the channel pack as supplied. Enable separate grates only when they are purchased separately.
Why are two short runs rounded separately?
The calculator does not assume offcuts retain suitable connections or can be reused elsewhere. Each run gets its own whole-section allowance.
Does every run need two end caps?
Not necessarily. Enter fittings from the actual connected layout; no automatic cap or outlet rule is applied.
What concrete dimensions should I enter?
Use the specified installation detail for the selected channel and intended loading. The tool estimates volume and does not prescribe the detail.
Does excavation include the bedding depth?
Enter the total assessed trench depth, including all necessary depth. The calculator does not add another bedding allowance to it.
Can I print the estimate for free?
Yes. Calculate and select Print / Save PDF. No account or email signup is required.