Rectangular • Trapezoidal • U-Channel
Use this Concrete Channel Calculator to estimate concrete for rectangular drainage channels, trapezoidal open channels and semicircular U-channels. Enter channel length and section dimensions to calculate concrete cross-sectional area, cubic feet, cubic yards, bags and optional ready-mix cost.
Rectangular, trapezoidal, U-channel and known-section-area calculators.
Flat base with two vertical side walls.
Estimate a sloped open channel lining.
Wall thickness is applied horizontally for estimating. Exact normal-to-slope thickness can require a drawing-based takeoff.
Semicircular channel with constant radial shell thickness.
Use concrete cross-sectional area from project drawings.
A channel is a continuous section, so concrete quantity is calculated from the concrete cross-sectional area × total length. For lined channels, the interior waterway is a void and must be removed from the outside concrete section.
Divide cubic feet by 27 to convert to cubic yards.
For a flat base and two vertical walls, the calculator uses outer rectangle minus inside void.
W = inside width, D = inside depth, t = wall thickness, b = base thickness.
The inside trapezoid area equals the average of top and bottom widths multiplied by depth. The calculator estimates a larger outer trapezoid and subtracts the inside area.
A true semicircular U-channel with constant radial shell thickness is one-half of an annulus.
Multiply the shell area by channel length for concrete volume.
Vertical walls and flat base.
Sloped drainage-channel lining.
Curved semicircular shell.
Convert total run to cubic yards.
Long drainage channels can use a large quantity of concrete even when the lining is relatively thin. Split the project wherever width, depth, wall thickness or base thickness changes. Transitions, drops, catch basins, aprons, headwalls and outlet structures should be calculated separately.
The optional cost field estimates ready-mix material only. Excavation, grading, reinforcement, forms, pumping, joints, curing, delivery fees and labor can be additional. For pumping needs, use the Concrete Pump Capacity Calculator.
Short repairs may use bagged concrete. Long channel runs can require many cubic yards, making ready-mix more practical. Use actual manufacturer bag yield in the fourth calculator.
This calculator estimates concrete quantity only. It does not calculate flow capacity, Manning's equation, velocity, freeboard, stormwater runoff or erosion control. Hydraulic and structural design should follow the project engineering requirements.
Rebar and joint systems are separate from concrete volume. Estimate reinforcement with the Concrete Rebar Calculator. After placement, use the Concrete Cure Time Calculator for curing schedule planning.
For technical concrete information and construction education, consult the American Concrete Institute and the National Ready Mixed Concrete Association.
Channel concrete equals the outer concrete section minus the interior void, multiplied by total length.
Common questions about drainage channels, U-channels and concrete quantity.