HYDRONIC PIPE SIZE CALCULATOR
How to Use the Hydronic Pipe Parameter Calculator
This calculator solves for unknown hydronic pipe parameters using the Darcy-Weisbach equation. Water flow rate is always required as the primary input. Follow the three steps below:
Step 1 — Select your fluid and pipe material. Choose between Chilled Water (6°C), Heating Hot Water (60°C), or Condenser Water (29.5°C). Then select either Copper Type B or Mild Steel Schedule 40. Fluid properties are automatically applied based on your selection.
Step 2 — Choose what you want to find. There are three solve modes:
Find Pipe Size — enter your flow rate and a maximum allowable pressure drop. Optionally enter a maximum velocity to apply a second constraint. The calculator returns the smallest standard pipe size that satisfies your limits.
Find Pressure Drop — enter your flow rate and select a pipe size. The calculator returns the pressure drop per metre of pipe and the flow velocity.
Find Velocity — enter your flow rate and select a pipe size. The calculator returns the velocity and pressure drop.
Step 3 — Enter your known values and tap Calculate. Results are displayed instantly on the right panel, including velocity, pressure drop, Reynolds number, friction factor, and flow regime. A colour-coded status indicator confirms whether the velocity falls within the recommended 0.7–3.0 m/s guideline.
To save or share your results, use the Print / Save as PDF button in the top-right corner.
