When fluid flows through a pipe it loses energy because of friction against the walls and extra turbulence in fittings and valves. That lost energy appears as a pressure drop the pump has to overcome. This calculator does the Darcy–Weisbach maths for you—factoring in pipe roughness, length, fittings, fluid density & viscosity—and outputs:

• Velocity and Reynolds number – confirms laminar or turbulent flow.
• Friction factor f via the Colebrook‑White equation.
• ΣK minor‑loss coefficient for your elbows, tees, valves, etc.
• Total pressure drop in kPa | bar | psi and equivalent head loss in metres.