Pipe Flow Velocity Calculator

Why smaller pipes mean faster flow

The continuity equation states that flow rate equals cross-sectional area times velocity for an incompressible fluid like water - forcing the same flow rate through a smaller pipe necessarily speeds up the flow inside it.

Worked example

For 0.05 m³/s flowing through a 200mm diameter pipe:

V = 0.05 / (π x 0.1²) = 1.592 m/s

Pipe sizing has to balance flow velocity carefully - too slow risks sediment settling out in the pipe, while too fast risks erosion damage and excessive pressure loss, which is why civil engineers check calculated velocity against acceptable design ranges when sizing water and drainage pipes.