Pipe Friction Loss Calculator
Calculate friction head loss and pressure drop in a pipe from flow rate, diameter, length and material. Uses Darcy–Weisbach with the Colebrook friction factor, or Hazen–Williams for water, with optional minor (fitting) losses and metric or imperial units.
Input
Pipe
Internal bore, not the nominal or outside diameter.
Sets the roughness (Darcy–Weisbach) or C-factor (Hazen–Williams) for a new pipe. Aged pipe is rougher.
Optional. Sum of K-values for elbows, valves and entrances (head = ΣK·V²/2g).
Fluid
Output
| Property | Value |
|---|---|
| No data yet | |
More ways to use this tool
REST API
curl -X POST https://api.iotools.cloud/v1/tool/pipe-friction-loss-calculator \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"method": "darcy",
"flowRate": "100",
"flowUnit": "lpm",
"diameter": "50",
"diameterUnit": "mm",
"length": "100",
"lengthUnit": "m",
"material": "steel",
"fluid": "water20",
"minorK": "0"
}'Swap in your own key from your account. The tool's fields are the body — no wrapper.
Ask an AI agent
Use the IOTools `pipe-friction-loss-calculator` tool (Pipe Friction Loss Calculator) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.
Embed widget
<iframe
src="https://iotools.cloud/embed/pipe-friction-loss-calculator/"
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title="Pipe Friction Loss Calculator — iotools.cloud"
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allow="clipboard-write"
style="width:100%;border:1px solid #e5e7eb;border-radius:12px;overflow:hidden"></iframe>
<script src="https://iotools.cloud/embed.js" async></script>Drop this into your own page — free, no key required, just a link back.
| Cost per API/MCP call | From 5 credits |
|---|---|
| Need more credits? | View pricing |
Also available with
Guides
Every fluid moving through a pipe loses energy to wall friction. That loss shows up as head loss (metres of fluid) or pressure drop, and it determines how big a pump you need or how small a pipe you can get away with. This calculator computes both from the flow rate, pipe size, length and material.
How to use it
- Choose a method: Darcy–Weisbach works for any fluid; Hazen–Williams is a simpler empirical formula for water only.
- Enter the flow rate, the pipe's inside diameter and its length, in whichever units you have.
- Pick the pipe material. Roughness (or the C-factor) is filled in for new pipe; choose Custom to enter your own.
- For Darcy–Weisbach, choose a fluid preset or enter a custom density and viscosity.
- Add a fittings coefficient (ΣK) if you want elbows, valves and entrances included.
The formulas
Darcy–Weisbach: h_f = f · (L/D) · V²/2g. The friction factor f is 64/Re for laminar flow and is solved from the Colebrook–White equation for turbulent flow; the 2,300–4,000 transitional band is blended between the two. Hazen–Williams (SI): h_f = 10.67 · L · Q^1.852 / (C^1.852 · D^4.87). Fitting losses are h_m = ΣK · V²/2g. Pressure drop is ρ·g·h.
Tips
- Use the actual inside diameter; nominal pipe sizes differ from the bore, and the loss scales roughly with the fifth power of diameter.
- Roughness values are for new pipe. Old, scaled pipe can have a much higher roughness and C-factor loss.
- Velocities above about 3 m/s (10 ft/s) in water lines usually signal noise, erosion or water-hammer risk.
Privacy
Everything runs in your browser. Your inputs are never sent to a server.
Related tools
Check the flow regime with the Reynolds Number Calculator, and convert units with the Pressure Converter.