Water hydraulics
Bore from target velocity
- where
- internal pipe diameter (m; the calculator shows mm)
- volume flow (m³/s; any unit you pick is converted)
- target velocity (m/s)
Explain this equation
Works out the internal bore needed to carry a given flow at a chosen velocity. Use it as a starting point for picking a water pipe size.
q is the volume flow. v is the target velocity you choose. d is the internal bore that achieves it.
It is the velocity equation rearranged. Flow divided by velocity gives the cross-sectional area. Converting area back to diameter means dividing by π / 4 and taking the square root. The calculator shows mm.
Sense check: 12 L/min at 1 m/s needs about 16 mm bore. Because of the square root, doubling the flow only increases the bore by about 41%.
Watch out: round up to a real pipe and check pressure loss. Not for gas pipe sizing.
Enter your values to see the result.
Good to know
Select an available pipe and check pressure loss and application limits. Not a gas-pipe sizing method.
Sources
Results are arithmetic only. Worked examples are not recommended design settings. This library does not provide automatic gas pipe selection, live gas tightness tests, purging procedures, combustion acceptance limits, installation approval or commissioning certification. Manufacturer data and the applicable current method remain essential.