Pipe Flow Rate Calculator
Calculation Results
Gallons per Minute (GPM)
0
Cubic Feet per Second (CFS)
0
Liters per Minute (LPM)
0
Cubic Meters per Hour (m³/h)
0
How to Calculate Flow Rate in a Pipe
Understanding how to calculate flow rate is essential for plumbing, irrigation, and industrial engineering. The flow rate ($Q$) represents the volume of fluid passing through a specific point in a pipe per unit of time.
The Basic Flow Rate Formula
The standard formula for calculating the flow rate in a circular pipe is:
Q = A × v
Where:
- Q: Flow Rate (volume per time)
- A: Cross-sectional Area of the pipe
- v: Velocity of the fluid
Step-by-Step Calculation Guide
- Determine the Internal Diameter: Measure the inside diameter of the pipe. If you have a 2-inch pipe, ensure you are using the actual internal measurement, as wall thickness can vary.
- Calculate the Area: Use the formula for the area of a circle: $A = \pi \times r^2$. Note that $r$ is the radius (half the diameter). Convert your measurement to feet for standard imperial calculations.
- Measure Velocity: Determine how fast the fluid is moving in feet per second (fps).
- Multiply: Multiply the area by the velocity to get the flow rate in cubic feet per second (CFS).
- Convert Units: Convert CFS to Gallons Per Minute (GPM) by multiplying by 448.83.
Practical Example
Imagine you have a pipe with an internal diameter of 4 inches and water flowing at 6 feet per second.
- Radius: 2 inches = 0.1667 feet
- Area: $\pi \times (0.1667)^2 = 0.0872$ square feet
- Flow (CFS): $0.0872 \times 6 = 0.523$ CFS
- Flow (GPM): $0.523 \times 448.83 = 234.7$ GPM