Pipe Flow Velocity Calculator
Calculate the mean fluid velocity in a pipe from its volumetric flow rate and inside diameter (or the flow rate a pipe carries at a given velocity), using the continuity equation V = Q/A. Works in metric or imperial units and checks the result against common piping design velocity guidelines.
Input
Pipe
Internal bore, not the nominal or outside diameter.
Output
| Property | Value |
|---|---|
| No data yet | |
| Application | Range (m/s) | Range (ft/s) | This Flow |
|---|---|---|---|
| No data yet | |||
Common rule-of-thumb velocity ranges used when sizing pipework, for reference.
Guides
The Pipe Flow Velocity Calculator finds the mean fluid velocity in a pipe from its volumetric flow rate and inside diameter, or works backwards to find the flow rate a pipe carries at a target velocity — the everyday check for sizing plumbing, HVAC ductwork, or a pump discharge line.
How to use it
- Choose what you're solving for — velocity from flow rate, or flow rate from velocity.
- Enter the flow rate (in L/min, L/s, m³/h, m³/s, US GPM, or CFM) or the velocity (m/s or ft/s), depending on the mode.
- Enter the pipe's inside diameter — the actual internal bore, not the nominal size stamped on the pipe (which is usually smaller than the true bore for schedule-rated pipe).
The result shows velocity and flow rate in both metric and imperial units, plus the flow area and the formula used. A reference table checks your result against common rule-of-thumb velocity ranges used in piping design.
The continuity equation
For an incompressible fluid in a full pipe, volumetric flow rate equals velocity times cross-sectional area:
Q = V × A ⇔ V = Q / Awhere A = π × D² / 4 for a circular pipe of inside diameter D. This calculator uses that relationship directly — for example, 100 L/min (0.001667 m³/s) through a 50 mm pipe (area 0.001963 m²) gives a velocity of 0.001667 / 0.001963 = 0.849 m/s.
Why velocity matters for pipe sizing
Too slow, and solids can settle out or air pockets can form; too fast, and you get excessive friction loss, erosion, water hammer risk, or noise. That's why piping codes and design guides publish target velocity ranges by application — a pump suction line is kept slower (0.5–1.0 m/s) than a discharge line (1.5–3.5 m/s), and compressed air or steam lines run much faster still. This tool flags which of those common ranges, if any, your result falls into.
Does this account for friction loss or pressure drop?
No — this is the continuity equation only (a purely geometric relationship between flow and velocity). Friction loss depends on pipe roughness, length, and fittings; use a dedicated head-loss or pressure-drop calculation for that, and check whether the flow is laminar or turbulent first since that changes which friction formula applies.
What if my pipe isn't circular?
This calculator assumes a circular cross-section. For a rectangular duct or an arbitrary shape, compute the flow area yourself (or use the Reynolds Number Calculator, which supports rectangular ducts) and divide flow rate by that area directly.
Everything runs in your browser; no inputs are sent to a server.
Use it from code
From 3 credits per callREST API
curl -X POST https://api.iotools.cloud/v1/tool/pipe-flow-velocity-calculator \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"inputMode": "velocity",
"flowRate": "100",
"flowUnit": "lpm",
"pipeDiameter": "50",
"lengthUnit": "mm"
}'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-flow-velocity-calculator` tool (Pipe Flow Velocity Calculator) on this input:
YOUR_INPUT_HEREPaste this at any agent connected to the IOTools MCP server, then add your input.