Work out water velocity in pipe instantly with clear inputs, formula shown and shareable results.
Velocity is volumetric flow divided by cross-sectional area. The Reynolds number, velocity times diameter divided by kinematic viscosity, confirms the flow regime: water in building services is almost always fully turbulent, above 4000, which is why turbulent friction correlations apply.
Velocity
V = Q / A, A = pi D² / 4
Reynolds number
Re = V D / kinematic viscosity, about 1.0 x 10^-6 m²/s for water at 20 °C
V = Q / A, A = pi D² / 4. Velocity is volumetric flow divided by cross-sectional area.
Above roughly 2 m/s copper and steel pipes become audible, and above 3 m/s erosion-corrosion becomes a real risk, particularly at bends and in soft water.
This calculator takes 2 inputs: Flow rate, Internal diameter. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.