Friction Loss Calculator

Available pressure is a budget, and every foot of pipe is a teller taking a cut. Sizing a line well means making sure the money still arrives at the last tap - and the tariff is the friction the bore charges to move the flow.

Friction Loss Calculator works that bill with the Hazen-Williams formula: the loss per hundred feet, then the total over your run.

• Hazen-Williams: Standard engineering method.
• Per 100 ft + total: Compare and sum.
• Dual units: psi, bar, feet and metres of head.
• Real bores: Built-in material tables or your own bore.
• Velocity check: Loss and speed together.
• Export: Text, CSV or JSON report.

1. Enter the flow the line must carry.
2. Pick the material and size, or type an internal bore.
3. Set C for the pipe age and type.
4. Enter the run length (straight + effective fittings).
5. Read the loss in psi and metres head.

Example 1. 4 GPM through 3/4 in PEX for 60 ft loses roughly 2.3 psi - fine within most residential budgets.

Example 2. Pushing 8 GPM through a 1/2 in line burns about 14 psi per 100 ft and screams - step the size up.

Example 3. 22 LPM in 20 mm PVC with C 150 over 30 m costs about 4.2 psi of head before anything else.

• Budget-first: Loss answered in psi.
• Real bores: Material tables built in.
• Both systems: Metric and imperial figures.
• Aging check: C factor shows the decline.
• Free and private: No uploads, no logging.