When to use this calculator
Estimate straight-pipe friction head loss from an entered Darcy factor. Use Darcy rather than Fanning friction factor. Fittings and entrance losses are excluded.
Explore the fluids & flow calculators for other questions in this topic. For a related calculation, use the Density Calculator: Calculate average material density from mass and volume.
PUTTING IT INTO PRACTICE
Darcy Weisbach Head Loss: a worked example
The values below are an illustrative example, not a recommendation. Replace them with measurements or assumptions that match your question.
| Input | Example value |
|---|---|
| Darcy friction factor | 0.02 |
| Pipe length (m) | 100 |
| Internal diameter (m) | 0.1 |
| Mean speed (m/s) | 2 |
| Gravity (m/s²) | 10 |
| Result | 4 m of fluid |
- Check the input labels and enter the example values above.
- Apply the relationship: Head loss = Darcy factor × length/diameter × speed²/(2g).
- The result is 4 m of fluid, rounded for display.
How to interpret your result
Use Darcy rather than Fanning friction factor. Fittings and entrance losses are excluded.
Use the fluid properties at the relevant conditions. Gauge pressure is measured relative to a reference and differs from absolute pressure. Average flow velocity and characteristic length must match the geometry being modelled.
Frequently asked questions
Should hydrostatic pressure be added to atmospheric pressure?
Add the surface absolute pressure when an absolute result is needed. The basic liquid-column calculation alone gives the pressure increase with depth.
When is the darcy weisbach head loss calculator useful?
Estimate straight-pipe friction head loss from an entered Darcy factor. Use Darcy rather than Fanning friction factor. Fittings and entrance losses are excluded.
How do I use the darcy weisbach head loss calculator?
Enter darcy friction factor, pipe length (m), internal diameter (m), mean speed (m/s), gravity (m/s²). The result updates automatically. Use the units shown beside each input; the example values illustrate the method.
Which formula does this calculator use?
Head loss = Darcy factor × length/diameter × speed²/(2g).
What should I check before using the result?
Use Darcy rather than Fanning friction factor. Fittings and entrance losses are excluded.
How are results rounded?
Scalar numbers display up to six decimal places, with scientific notation for very large or small values. Text, fraction, date and schedule outputs use the format described on the tool. Intermediate calculations use JavaScript floating-point arithmetic. Keep sensible precision for your measurements.
Further reading
For background on this topic, see OpenStax: fluids, density and pressure ↗. This is a topic reference, not an external review or endorsement of this tool.
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