How Hydraulic Diameter Calculator Works
Calculate hydraulic diameter for circular and non-circular flow passages from flow area and wetted perimeter. The calculation runs locally in your browser and does not require an account.
How to use it
- Enter values using the units shown.
- Check your source measurements and assumptions.
- Calculate and compare scenarios before making a decision.
Limitations
Hydraulic Diameter Calculator is an estimation aid. For a critical result, compare the inputs and output with the applicable standard, manufacturer data, project specification, site condition, or qualified professional review.
When hydraulic diameter is useful
Hydraulic diameter lets many pipe-flow relationships be adapted to non-circular passages such as rectangular ducts, channels and annular spaces. The key inputs are the actual open flow area and the wetted perimeter. If a passage contains internal obstructions, partially filled flow or changing geometry, use the area and wetted perimeter that correspond to the operating condition rather than a nominal outside dimension.
This result can be used as an input to Reynolds-number and friction-factor calculations, but it does not by itself determine pressure loss. Surface roughness, fluid viscosity, flow regime, fittings and entrance effects can also matter. For critical systems, use a validated hydraulic model or engineering standard.