Use this engineering calculation for a transparent preliminary estimate or independent arithmetic check when geometry, materials, loads, operating conditions, and units are defined consistently.

Runoff Coefficient

Required number input.

Rainfall Millimeters Per Hour (mm/h)

Required number input.

Area Hectares (ha)

Required number input.

Rational-method runoff peak Q=C i A/360 in m³/s for rainfall intensity in mm/h and drainage area in hectares. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Peak Cubic Meters Per Second (m³/s)

The resulting peak cubic meters per second returned as a number.

• Peak flow, reservoir, and demand calculations depend on watershed or service boundaries, rainfall and climate records, runoff assumptions, losses, storage, operating rules, population, seasonality, leakage, and regulatory design events.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Check assumptions against drawings, measurements, current material data, and the applicable design code. Apply required load combinations and safety factors, then obtain qualified review and testing for consequential designs.

• Earthwork Volume Average End Area

  Earthwork volume between two sections by the average-end-area method; assumes linear area change.

• Extrusion Pressure

  Ideal frictionless extrusion pressure from a supplied mean flow stress times ln(initial area/final area); actual die pressure may be higher.

• Flow Rate Velocity Area

  Volumetric flow rate from mean cross-sectional velocity and flow area.