Flow Rate Calculator

Calculate fluid flow rate through a pipe.

Enter Pipe Parameters

For circular pipes

Solve For

Pipe Diameter (d)

Flow Velocity (v)

m/s

Flow Rate (Q)

L/s

Cross-Sectional Area (A)

m²

m³/s

L/min

m³/h

gal/min

Reynolds Number (Water @ 15°C)

→ Full Reynolds Number Calculator

Enter your pipe parameters above and tap Calculate to see the result.

Flow Rate Formulas

Q = A × v
A = π × (d/2)²
v = Q / A

Q: Flow rate (m³/s, L/s)
A: Cross-sectional area (m²)
v: Flow velocity (m/s)
d: Pipe diameter (m)

Related Calculators

Typical Flow Velocities

Water in pipes: 0.5–3 m/s (residential/commercial)

Air in ducts: 5–15 m/s (HVAC systems)

Oil pipelines: 1–2 m/s (viscous fluids)

Pro Tips

Results update as you type — change any field to see the effect immediately.

Check that every value uses the same unit before comparing results.

Use the copy button to paste the flow rate figures into a note or spreadsheet.

Nothing is sent to a server, so you can use this with private figures.