🚰 Friction Loss Calculator
Estimate the pressure lost to friction as fluid flows through a pipe, using the Hazen-Williams equation.
What this calculator does
As fluid moves through a pipe, friction against the pipe walls causes a gradual loss of pressure along its length. This calculator estimates that pressure loss using the widely used Hazen-Williams equation, common in water supply and fire sprinkler system design.
The formula
Friction loss per foot of pipe is P = 4.52 × Q^1.85 / (C^1.85 × d^4.87), where Q is the flow rate in gallons per minute, d is the pipe’s inside diameter in inches, and C is the Hazen-Williams roughness coefficient (higher C means a smoother pipe with less friction). Total loss is this per-foot value multiplied by the pipe length.
The Hazen-Williams equation is intended for water flowing at typical ambient temperatures and does not apply well to other fluids or very high velocities. This calculator is for general planning and educational purposes; final piping design should follow applicable codes and be reviewed by a qualified engineer.