Pipe Flow Calculator
Enter your pipe diameter and average fluid velocity to find the volumetric flow rate, cross-sectional area, and mass flow rate.
What This Calculator Does
This tool finds the volumetric and mass flow rate of a fluid moving through a circular pipe when you know the pipe’s inside diameter and the average velocity of the fluid across the cross-section.
The Formula
The continuity relationship for incompressible flow is Q = A × v, where Q is volumetric flow rate, A is the pipe’s cross-sectional area (πr², calculated from the inside diameter), and v is the average flow velocity. Mass flow rate is then ṁ = ρ × Q, where ρ is the fluid density.
- This assumes fully-developed, single-phase flow with a uniform average velocity across the pipe cross-section.
- Real velocity profiles vary across the pipe (faster at the center in laminar flow), so this gives the bulk average result used in standard engineering practice.
These are standard fluid-mechanics relationships used for general engineering planning and educational purposes; for critical system design, consult applicable piping codes and a qualified engineer.