Weir Flow Calculator

Calculate open channel flow rate over rectangular and V-notch (triangular) weirs for flow measurement.

Water level above the weir crest.
mm
Width of the rectangular weir opening. 0 for V-notch.
mm
Full angle for V-notch weir. 90° is most common. 0 for rectangular.
degrees
Rectangular: 0.60-0.65. V-notch: 0.58-0.62.

Results

Flow (Rectangular)-L/s
Flow (V-notch)-L/s
Active Flow Rate-L/s
References: ISO 1438 — Thin-Plate Weirs; USBR Water Measurement Manual