Friction Loss

Formula and source

Hazen-Williams head loss (feet of head): hL = 10.44 × Q^1.852 / (C^1.852 × D^4.87) per 100 ft (water; English units; the NFPA-13 4.52 coefficient gives psi, feet = psi × 2.307). Darcy-Weisbach for gas and other fluids.

Hazen-Williams (AWWA M11, 5th ed., by name). Darcy-Weisbach: classical fluid mechanics.

Audience

This tile is built for plumbers and the adjacent professions in the Plumbing and Gas group. The interactive calculator runs entirely in your browser. No account, no fee, no advertising, no tracking.

Related tools

• Pipe Sizing
• Pump Sizing
• Static Pressure Loss in Piping
• Hydrant Flow

Posture

Rough Logic answers the math question the working professional asks on the job. The site is a calm, fast, ad-free, account-free, ever-free reference. It does not interpret code. It does not replace the licensed professional. It does not store your inputs. The Authority Having Jurisdiction governs all installations and inspections.