Hydraulic Diameter

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Calculator / Last modified by AndrewS on 2015/11/03 15:18
Circular Tube
Square Duct
Rectangular Duct (fully filled)
Channel of Water or Partially Filled Rectangular Duct

Hydraulic diameter (DH) is a commonly used term when handling flow in non-circular tubes and channels. It is mainly used for calculations involving turbulent flow. Hydraulic diameter is also used in calculation of heat transfer in internal flow problems.

For a fully filled duct or pipe whose cross section is a regular polygon, the hydraulic diameter is equivalent to the diameter of a circle inscribed within the wetter perimeter.


This calculator includes the computations for Hydraulic Diameter for the following shapes of conduits:

  • Circular Tube
  • Annulus
  • Square Duct
  • Rectangular Duct
  • Channel of Water


  • "Hydraulic Diameter." Wikipedia. Wikimedia Foundation. <https://en.wikipedia.org/wiki/Hydraulic_diameter>.