Plumbing & Water Calculators
Hydraulic tools for plumbers, installers and designers. Flow calculations use the internal diameter and the Darcy-Weisbach/Swamee-Jain model for pressure loss; every assumption (water at 20 °C, straight-pipe friction) is stated on the page.
Flow & Sizing
Velocity checks, pipe sizing from flow limits, and water volume in runs.
- Pipe Flow CalculatorCalculate water velocity in a pipe from flow rate and internal diameter, in m/s, ft/s and gpm — with the supply design range and hammer/erosion warnings.
- Pipe Size CalculatorFind the minimum pipe internal diameter for a flow rate and velocity limit, snapped to the next standard trade size, with the actual velocity shown.
- Pipe Volume CalculatorCalculate the water volume and weight inside a pipe run from internal diameter and length — for flushing, disinfection, glycol batching and dead-leg waste.
Pressure & Storage
Pressure loss along runs and tank capacity for storage and dosing.
- Pipe Pressure Drop CalculatorCalculate pressure loss in a pipe run: Darcy-Weisbach head loss with the Swamee-Jain friction factor, in metres, kPa, psi and bar — laminar and turbulent.
- Tank Volume CalculatorCalculate tank capacity in litres, gallons and barrels from cylindrical or rectangular internal dimensions, with full-water weight for floor loading.