Pipe Flow Rate Calculator
A simple and effective tool for plumbers, HVAC technicians, and engineers. Quickly calculate the volumetric flow rate of water in a pipe based on its size and the fluid's velocity.
The Fundamentals of Fluid Dynamics in Plumbing
Understanding flow rate is essential for designing and troubleshooting any plumbing or fluid transport system. The flow rate, or the volume of fluid that passes through a point per unit of time, determines the efficiency and effectiveness of the system. Whether you're sizing a pump, designing an irrigation system, or ensuring a building has adequate water pressure, calculating the flow rate is a fundamental first step. An incorrectly sized pipe can lead to issues like low pressure, high energy consumption for pumps, or even damage to the system due to excessive velocity (known as "water hammer").
The Core Formula: Q = A × V
The calculation for volumetric flow rate is based on a simple and elegant equation from fluid dynamics: Flow Rate (Q) = Cross-Sectional Area (A) × Velocity (V).
- Cross-Sectional Area (A): This is the area of the inside of the pipe. For a circular pipe, it's calculated using the formula for the area of a circle, A = πr², where 'r' is the internal radius of the pipe. It's crucial to use the *internal* diameter, not the external one.
- Velocity (V): This is the speed at which the fluid is moving through the pipe. It's often determined by the pump's power or the system's design pressure.
This tool takes your inputs for diameter and velocity, calculates the internal area of the pipe, and then multiplies it by the velocity to find the flow rate. It also handles the unit conversions (e.g., from square feet per second to gallons per minute) to give you a practical, usable number.