This friction loss calculator will help you determine the pressure drop in a pipe or fluid system due to friction.
This parameter is vital to most fluid flow calculations and system design, especially for plumbing, HVAC, and industrial piping.
Friction loss is a function of pipe diameter, flow velocity, pipe roughness, and fluid properties. The tool considers both laminar and turbulent flow while performing the calculations.
Different pipe materials and flow conditions also affect the results using the Darcy-Weisbach or Hazen-Williams equations. Read on to understand what friction loss is and how to use the friction loss formulas.
Friction Loss Calculator
Formula details, applications & worked example
Description: Head loss (hf) is the energy loss per unit weight of fluid due to friction along a straight pipe.
- hf: head loss (m of fluid)
- f: Darcy friction factor (dimensionless)
- L: pipe length (m)
- D: pipe diameter (m)
- v: velocity (m/s)
- g: gravitational acceleration (≈ 9.81 m/s²)
Real-world applications
Municipal water mains
Estimate pressure loss in supply mains for pump sizing and service pressure.
Industrial process piping
Design pipes, pumps and heat exchangers where losses impact energy costs.
HVAC & chilled water
Balance flow, pump power and energy costs in long heating/cooling runs.
Irrigation & sprinklers
Ensure uniform distribution and proper pump selection in agriculture.
Worked example — narrative problem
Problem: Maplevale installs a 100 m water main, velocity = 2.00 m/s, D = 0.15 m, f = 0.020. Find hf.
- Formula:hf = f (L/D) (v²/2g)
- Knowns:f=0.020, L=100m, D=0.150m, v=2.00 m/s, g=9.81 m/s²
- L/D:100/0.15 = 666.67
- f·L/D:0.020 × 666.67 = 13.33
- Multiply v²:13.33 × 4 = 53.33
- Divide by 2g:53.33 / 19.62 ≈ 2.718 m
Reference Table
| Parameter | Symbol | Typical Values / Notes | Units |
|---|---|---|---|
| Head loss | hf | Energy loss per unit weight of fluid | m |
| Darcy friction factor | f | 0.01 – 0.06 (depends on Reynolds no. & roughness) | dimensionless |
| Pipe length | L | Actual straight length of the pipe | m |
| Pipe diameter | D | Inside diameter (smaller → more loss) | m |
| Velocity | v | Flow speed, typically 1 – 5 m/s in water mains | m/s |
| Gravity | g | Standard acceleration due to gravity | 9.81 m/s² |
| Reynolds number | Re | Laminar: Re < 2000, Turbulent: Re > 4000 | dimensionless |
| Relative roughness | ε / D | Ratio of roughness height to pipe diameter | dimensionless |
What is friction loss in a pipe system?
Friction loss is the pressure drop that happens when fluid flows through a pipe because of resistance from the pipe walls.
Why is calculating friction loss important?
With the help of friction loss, we can determine the actual size of the pump based on the flow rate
How does pipe diameter affect friction loss?
The effect of pipe diameter on friction loss is that larger diameters reduce friction loss, while smaller diameters increase it.