Perda carga (Hazen-Williams)
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
About this calculator
The Hazen-Williams head loss calculator estimates pressure drop in water pipelines using pipe diameter, flow rate, and roughness coefficient. This empirical formula relates the water volume transported, internal pipe diameter, and flow resistance determined by the internal surface condition.
The equation J = 10.67·Q^1.85/(C^1.85·D^4.87) calculates head loss (J) in meters per kilometer. Q is the flow rate in liters per second, C is the Hazen-Williams coefficient (ranging from 80 to 150), and D is the pipe diameter in meters. The method is widely used in water distribution and drainage system designs.
This tool is suitable for water supply system projects requiring pipeline sizing with acceptable losses. However, note that the formula assumes turbulent flow and is not recommended for liquids other than water. Selecting the C coefficient should consider pipe material and condition (new or worn).
Frequently asked questions
What is the C coefficient in the formula?
It represents the pipe roughness factor. Higher values indicate smooth surfaces (like PVC), while lower values correspond to worn pipes or rough materials.
Can this formula be used for liquids other than water?
No, it was developed specifically for water at around 20°C. For other liquids, use methods like Darcy-Weisbach with appropriate viscosity values.
Why is the diameter raised to 4.87?
This exponent reflects the non-linear relationship between diameter and head loss: larger pipes exponentially reduce pressure loss.
What units should I use for input and output?
Q in liters/second, D in meters. The result is head loss in meters per kilometer of pipe.