Pressure Drop Calculator
Calculate pressure drop and head loss using the Darcy-Weisbach equation for accurate pump sizing, energy analysis, and piping system design.
Steel: 0.045mm, PVC: 0.0015mm
Calculation Results
Enter parameters to calculate pressure drop
About Pressure Drop Calculations
This calculator uses the Darcy-Weisbach equation, the most accurate method for calculating pressure drop in pipes: ΔP = f × (L/D) × (ρV²/2). This equation accounts for friction losses due to fluid viscosity, pipe roughness, flow velocity, and pipe geometry.
Key Calculation Steps
- 1. Calculate Velocity: V = Q / A, where A = π × D² / 4
- 2. Determine Reynolds Number: Re = ρ × V × D / μ
- 3. Find Friction Factor: Based on flow regime and roughness
- 4. Calculate Pressure Drop: ΔP = f × (L/D) × (ρV²/2)
- 5. Convert to Head Loss: h = ΔP / (ρ × g)
Input Parameters
- Flow Rate: Volumetric flow (L/s or GPM)
- Pipe Diameter: Internal diameter (mm or in)
- Pipe Length: Total straight pipe length (m or ft)
- Pipe Roughness: Material surface roughness
- Fluid Properties: Density and viscosity
Results Provided
- Pressure Drop: Friction loss (kPa or psi)
- Head Loss: Equivalent height (m or ft)
- Fluid Velocity: Average flow velocity
- Reynolds Number: Flow regime indicator
- Friction Factor: Darcy friction factor
Engineering Applications
- • Pump selection and sizing
- • Energy cost analysis
- • System optimization
- • Pipe sizing verification
- • HVAC system design
- • Water supply networks
- • Chemical process piping
- • Fire protection systems
Important Considerations
- • This calculation covers straight pipe friction losses only
- • Add fitting losses (elbows, valves, tees) for total system pressure drop
- • Consider elevation changes when calculating total head requirements
- • Include safety factors (typically 10-25%) for pump selection
- • Verify all calculations against applicable codes and standards
- • Account for pipe aging and fouling in long-term installations
Why Darcy-Weisbach?
The Darcy-Weisbach equation is preferred over the Hazen-Williams equation because it: applies to all fluids (not just water), covers all flow regimes, accounts for temperature effects through fluid properties, and provides greater accuracy across a wider range of conditions. It is the standard method in ASHRAE, ASME, and international engineering practice.