Pipe Flow Calculator

Formula

v = Q / A where Q = volumetric flow rate (m³/s) and A = pipe cross-sectional area (m²) = π·(D/2)².

Variables

• Q — flow rate (m³/h, converted to m³/s)
• D — pipe internal diameter (m)
• v — mean flow velocity (m/s)

Example

85 m³/h through a DN125 (0.125 m) pipe: A = π·(0.0625)² = 0.01227 m²; v = (85/3600)/0.01227 ≈ 1.92 m/s.

Application

Useful for preliminary pipe sizing, pump selection and checking whether a flow is within a reasonable velocity range for water service.

Limitations

This is a mean-velocity estimate. It does not account for friction loss, fittings, fluid properties or pressure drop. Full hydraulic design requires a qualified engineer.