Enter the actual flow rate and theoretical flow rate into the calculator to determine the Coefficient of Discharge. This calculator can also evaluate any of the variables given the others are known.

Coefficient Of Discharge Formula

The following formula is used to calculate the Coefficient of Discharge. 

Cd = Qa / Qt

Variables:

  • Cd is the Coefficient of Discharge (dimensionless)
  • Qa is the actual flow rate (m³/s)
  • Qt is the theoretical flow rate (m³/s)

To calculate the Coefficient of Discharge, divide the actual flow rate by the theoretical flow rate. The result is a dimensionless number that represents the efficiency of a system or device in allowing fluid flow.

What is a Coefficient Of Discharge?

A Coefficient of Discharge is a dimensionless number used in fluid mechanics and hydraulics, representing the efficiency of a system or device (like a valve, nozzle, orifice, etc.) in allowing fluid flow. It is the ratio of the actual flow rate to the theoretical flow rate, accounting for energy losses due to friction, re-direction, or turbulence. A higher coefficient indicates a more efficient system with less energy loss.

How to Calculate Coefficient Of Discharge?

The following steps outline how to calculate the Coefficient of Discharge (Cd).

  1. First, determine the actual flow rate (Qa) in cubic meters per second (m³/s).
  2. Next, determine the theoretical flow rate (Qt) in cubic meters per second (m³/s).
  3. Next, gather the formula from above: Cd = Qa / Qt.
  4. Finally, calculate the Coefficient of Discharge (Cd).
  5. After inserting the values for Qa and Qt into the formula and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

Actual flow rate (Qa) = 5 m³/s

Theoretical flow rate (Qt) = 8 m³/s