Pipe Flow Calculator | Flow Rate, Pressure Drop & Reynolds Number

Darcy-Weisbach is more accurate and works for all fluids and flow conditions. Hazen-Williams is an empirical formula simpler to use but valid only for water at normal temperatures and turbulent flow. Use Darcy-Weisbach for engineering accuracy; Hazen-Williams for quick water system estimates.

Reynolds Number predicts flow patterns. Re < 2100 is Laminar (smooth, parallel flow). Re > 4000 is Turbulent (chaotic mixing). The transition zone is 2100-4000. This determines which friction factor formula applies.

Use the pipe sizing mode: enter your required flow rate (GPM or L/s), pipe material (C-factor or roughness), and maximum acceptable pressure drop per unit length. The calculator solves for the minimum pipe diameter that meets the flow requirement without excessive friction loss.

Friction factor (f) quantifies energy loss due to pipe wall friction. For laminar flow, f = 64/Re. For turbulent flow, the Moody chart or Colebrook-White equation is used. This calculator computes friction factor automatically and uses it in the Darcy-Weisbach pressure drop equation.

Yes! In guest mode, you can export your calculations to JSON format. Sign in is required for PDF and CSV export. Click the export button to download your results. This is perfect for record-keeping, sharing with others, or importing into other tools.

Yes! Your calculation history is automatically saved. Guest users can save up to 50 calculations per workspace locally. Sign in for free to save up to 100 calculations per workspace, with access from any device when logged in.

Absolutely! The Pipe Flow / Pressure Drop Calculator is completely free with no sign-up required. Create a free account to unlock additional features like more calculation history, multiple workspaces, and the ability to access your saved data from any device.