Method: Pipe area = π × diameter² ÷ 4. Velocity = volumetric flow rate ÷ pipe cross-sectional area. The calculator converts the entered flow rate to m³/s and pipe diameter to metres before calculating velocity. The result represents average velocity in a completely full circular pipe. The velocity indicator is only a general screening guide. Acceptable velocity depends on fluid characteristics, pipe material, pressure, noise, erosion, water hammer, sediment transport and system-specific design requirements.