Pipe Flow Calculator
Size pipes, calculate flow velocity, or determine flow rate using the continuity equation. Get recommended velocities for different fluids.
Pipe Flow Calculator
Calculate pipe size, velocity, or flow rate
Required Pipe Diameter
50.0
mm
Standard size: 50mm (or 50mm next size up)
Flow Parameters
Diameter
50.0
mm
Velocity
2.00
m/s
Flow Rate
14.1
m³/h
Area
1,963.9
mm²
Recommended Velocity for Liquids
Current: 2.00 m/s
Continuity Equation
Q = flow rate, A = area, V = velocity, D = diameter
How to Use This Calculator
Choose what to calculate: pipe diameter, flow velocity, or volumetric flow rate. Enter the other two values along with the fluid type.
Select the fluid type (liquid, gas, or steam) to see appropriate velocity recommendations. The calculator warns if velocity is outside the recommended range.
For pipe sizing, the calculator shows the calculated diameter and suggests the nearest standard pipe size for easy specification.
Velocity Design Guidelines
Liquids (Water) - Design for 1-3 m/s (3-10 ft/s). Higher velocities for main headers, lower for branches. Avoid < 0.5 m/s to prevent settling.
Viscous Liquids - Lower velocities (0.5-2 m/s) to reduce pressure drop. Consider heating to reduce viscosity.
Gases - Higher velocities are acceptable: 15-60 m/s depending on pressure. Higher pressure allows higher velocity.
Steam - Saturated steam: 20-40 m/s. Superheated steam: 30-60 m/s. Avoid condensate accumulation in steam lines.
Frequently Asked Questions
How do I size a pipe for a given flow rate?
Use the continuity equation: Q = A × V. For a given flow rate and desired velocity, solve for diameter: D = √(4Q/πV). This calculator does this automatically and suggests standard pipe sizes.
What is the recommended velocity for water in pipes?
For water, typical velocities are 1-3 m/s (3-10 ft/s). Lower velocities may cause settling; higher velocities increase erosion, noise, and pressure drop. Economic velocity balances pipe cost vs pumping cost.
What velocity should I use for gas piping?
Gas velocities are typically 15-30 m/s for low pressure systems and 30-60 m/s for high pressure. Steam lines typically run 20-40 m/s for saturated steam and 30-60 m/s for superheated.
Why does the calculator show 'high velocity' warning?
High velocities can cause pipe erosion (especially with abrasive fluids), excessive noise, and high pressure drops requiring more pumping energy. Consider using a larger pipe size.
What is the continuity equation?
The continuity equation (Q = A × V) states that for incompressible flow, the volumetric flow rate equals the cross-sectional area times velocity. This is derived from conservation of mass.
How do I convert between GPM and m³/h?
1 GPM = 0.227 m³/h, or 1 m³/h = 4.403 GPM. This calculator handles unit conversions automatically when you switch between metric and imperial units.
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