Pipe Flow Calculator
Calculate flow rate and Reynolds number from pipe diameter and fluid velocity, and classify the flow as laminar, transitional, or turbulent.
- Free to use
- Accurate results
- No registration required
- Works on all devices
Enter your pipe diameter and flow velocity to find the flow rate, Reynolds number, and flow regime.
1000 kg/m³ for water at room temperature.
0.001 Pa·s for water at room temperature.
Your result
235.62
Flow rate
Flow rate (m³/s)0.004
Reynolds number1,00,000
Flow regimeTurbulent
Pipe cross-section area0.002
AI explanation
Formula
Flow rate Q = A × V (continuity equation); Reynolds number Re = ρVD/μWorked example
50mm pipe, 2 m/s water flow
| Field | Value |
|---|---|
| Pipe internal diameter (mm) | 50 |
| Flow velocity (m/s) | 2 |
| Fluid density (kg/m³) | 1000 |
| Fluid viscosity (Pa·s) | 0.001 |
| Pipe cross-section area | 0.001963 |
| Flow rate (m³/s) | 0.003927 |
| Flow rate | 235.62 |
| Reynolds number | 100000 |
| Flow regime | Turbulent |
Assumptions
- Re < 2300 is classified as laminar, 2300-4000 as transitional, and above 4000 as turbulent — standard thresholds for flow in a circular pipe.
Frequently asked questions
What is the Reynolds number used for?
It's a dimensionless number that predicts whether flow will be smooth (laminar) or chaotic (turbulent) — important because friction losses and mixing behavior differ significantly between the two regimes.
What's the difference between laminar and turbulent flow?
Laminar flow moves in smooth, parallel layers with little mixing; turbulent flow is chaotic with significant mixing. Most everyday pipe flows (like water in household plumbing) are turbulent.
I need the pressure drop too — is there a calculator for that?
Yes — see the Pressure Drop Calculator, which uses this same flow information to compute friction losses via the Darcy-Weisbach equation.