Calculator Inputs and Outputs
Inputs
- Reynolds number — example: 100000
- Relative roughness ε/D — example: 0.001
Results
- Darcy friction factor
- Fanning friction factor
Formula used
Swamee–Jain: f = 0.25/[log₁₀(ε/3.7D + 5.74/Re^0.9)]².
How to Use the Darcy Friction Factor Calculator
Enter the requested values, check the units and assumptions, then select Calculate Darcy Friction Factor. The built-in defaults provide a complete working example.
Formula
Swamee–Jain: f = 0.25/[log₁₀(ε/3.7D + 5.74/Re^0.9)]².
Understanding the Results
The primary answer appears first. Supporting outputs show related quantities, conversions, dates, costs, ratios, or intermediate values. Calculations keep additional precision before display rounding.
Accuracy Tips
- Use measured values and consistent units.
- Review assumptions, rates, timing, and efficiency inputs.
- Recalculate after changing any condition.
Important Note
This tool provides an informational estimate. Confirm critical financial, medical, construction, scientific, tax, legal, or safety decisions with an appropriately qualified professional.
Calculation Standards
This tool uses documented formulas and high-precision internal values. Displayed results may be rounded for readability. Review the assumptions and verify important decisions with a qualified professional.
Read our calculation methodology