Pipe Flow Guide
A practical note on the relationship between flow rate, diameter, and velocity.
What matters most
Pipe flow sizing is a geometry-and-speed problem: once two of the three values are known, the third can be derived from the continuity equation.
Common mistakes
- Using nominal pipe size instead of internal diameter.
- Ignoring the practical velocity range for the selected fluid.
- Confusing pipe sizing with pressure-loss calculation.
When to use the calculator
Use it for quick checks when laying out hydronic or air systems, or when comparing possible pipe sizes.