Volume Flow Rate Calculator
Calculate fluid flow based on pipe size and velocity, or volume and time.
Pipe Diameter & Flow Velocity
Total Volume & Time
Rectangular Duct Area & Velocity
Millimeters (mm)
Inches (in)
Meters (m)
Meters per second (m/s)
Feet per second (ft/s)
Calculation Results
Flow Rate (Cubic m/hr):
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Flow Rate (Liters/min):
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Flow Rate (Gallons/min):
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Flow Rate (Cubic m/s):
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Understanding Volume Flow Rate
Volume flow rate is a fundamental concept in fluid dynamics, engineering, and physics. It represents the volume of fluid that passes through a specific surface or conduit (such as a pipe or duct) per unit of time. It is commonly denoted by the symbol Q.
The Basic Formula
The most basic definition of volume flow rate is derived from the volume of fluid and the time it takes to accumulate or pass:
Q = V / t
Where:
- Q = Volume Flow Rate (e.g., m³/s)
- V = Volume of fluid (e.g., m³)
- t = Time (e.g., seconds)
Calculating Flow Rate from Velocity and Area
In piping systems and HVAC applications, it is often more practical to calculate flow rate based on the size of the conduit and the speed at which the fluid is moving. The formula for this is:
Q = A × v
Where:
- A = Cross-sectional Area of the pipe or duct (m²)
- v = Flow Velocity (m/s)
For Circular Pipes
Since pipes are circular, the area (A) is calculated using the diameter (d): A = π × (d/2)². Substituting this into the flow rate formula gives:
Q = π × (d/2)² × v
This calculator handles these conversions automatically, allowing you to input diameters in millimeters or inches and velocities in various units.
Common Units and Conversions
Flow rate is expressed in many different units depending on the industry:
- L/min (LPM): Common in hydraulics and water systems.
- GPM (Gallons Per Minute): Standard in the US for plumbing and pumps.
- m³/hr: Used in industrial process engineering and ventilation.
- CFM (Cubic Feet per Minute): Standard for HVAC airflow.
Note: 1 GPM (US) ≈ 3.785 LPM. 1 m³/hr ≈ 16.67 LPM.