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Pipe Friction Loss Calculator
Estimate straight-pipe friction loss with Reynolds number, flow regime, roughness, fluid properties, Darcy friction factor, head loss, and pressure drop.
This works right here on your device — nothing gets sent out.
Defaults approximate cool water in a smooth pipe. This calculates straight-pipe major loss; fittings, valves, elevation, and entrance effects are excluded.
Head loss
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Pressure drop
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Reynolds number
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Darcy factor / regime
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Model: Darcy–Weisbach. Laminar flow uses f = 64/Re; turbulent flow uses the explicit Swamee–Jain approximation to Colebrook–White. Transitional flow (Re 2,300–4,000) should be treated as uncertain.
How it works
- Enter pipe geometry, flow rate, wall roughness, and fluid properties.
- The calculator derives velocity and Reynolds number, then selects a Darcy friction factor.
- Review straight-pipe head loss and pressure drop; add fittings and elevation separately for a system total.
FAQ
What does this calculator estimate?
It estimates straight-pipe major head loss and pressure drop using Darcy–Weisbach, based on diameter, length, flow, roughness, density, and dynamic viscosity.
Does it include fittings and valves?
No. Elbows, tees, valves, entrances, exits, elevation changes, and other minor losses are excluded and must be added separately.
What is the Reynolds number used for?
It identifies the flow regime and helps select the Darcy friction-factor method. Results in the transitional range from about 2,300 to 4,000 are inherently uncertain.
How we compare
| Feature | Online Tool Store | Moody Chart Calculator | Engineering Toolbox |
|---|---|---|---|
| Darcy–Weisbach head loss | Yes | Yes | Yes |
| Custom fluid properties | Yes | Yes | Yes |
| Reynolds number and flow regime | Yes | Yes | Yes |
| Copyable browser result | Yes | Varies | Varies |
Use this for a transparent straight-pipe estimate; include minor losses and validate critical designs with appropriate engineering references.