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Rectangular Weir Flow Rate Calculator

The Rectangular Weir Flow Rate calculator is used to measure the water flow rate. The flow rate over a weir is a function of the head on the wei.



Flow Rate


  • g = Gravity Constant value (9.81 m/s²)
  • q = Flow rate
  • h = Head on the Weir
  • b = Width of the Weir
  • Cd = Discharge Constant

Defination / Uses

The Rectangular Weir Flow Rate is used to estimate the flow rates of rivers and canals in open channels. The water flow rate in rivers and canals is measured using our powerful online Rectangular Weir Flow Rate Calculator.

How to use rectangular weir flow rate calcultor?

There are only single step.

  • Add the values in their corresponding fields.

Thats it! You will get your answer in just a second.

This tool will help you to calculate more accurate results than manual calculation. The water flow rate over a rectangular contracted weir is calculated using this formula. The sides of this weir are straight up and down, and it has a rectangular aperture. The ditch or canal leading up to the weir is broader than the weir opening itself, resulting in a contracted weir. The water in the pool before the weir should be relatively calm and smooth. Underneath the water leaving the weir, there should be air (not trapped). The Length refers to the weir's bottom width. The height is calculated by measuring the distance between the bottom of the weir aperture and the top of the ponded water level behind the weir (not the water level right as it leaves the weir).