Water Flow Rate Calculator
Liters
Gallons (US)
Cubic Meters (m³)
Seconds
Minutes
Hours
Inches
Millimeters (mm)
Centimeters (cm)
Meters/Second (m/s)
Feet/Second (ft/s)
Calculated Flow Rate
Gallons Per Minute (GPM):
–
Liters Per Minute (LPM):
–
Cubic Meters Per Hour (m³/h):
–
Liters Per Second (L/s):
–
Water Flow Rate Calculator Online
Whether you are designing an irrigation system, checking your home plumbing pressure, or engineering a fluid dynamics system, knowing the water flow rate is essential. This online calculator provides two distinct methods for determining flow rate: the "Bucket Method" (Volume/Time) and the "Pipe Method" (Hydraulics).
How to Calculate Water Flow Rate
Flow rate ($Q$) is defined as the volume of fluid ($V$) that passes through a surface per unit of time ($t$). Depending on the data you have available, you can calculate it in two ways:
Method 1: The Volume & Time Calculation
This is the most common method for measuring flow from a faucet, hose, or showerhead. It involves measuring how long it takes to fill a container of a known volume.
Formula: $$Q = \frac{V}{t}$$
- $Q$: Flow Rate
- $V$: Volume (e.g., Gallons or Liters)
- $t$: Time (e.g., Seconds or Minutes)
Example: If a 5-gallon bucket fills in 30 seconds, the flow rate is 10 Gallons Per Minute (GPM).
Method 2: The Pipe Diameter & Velocity Calculation
This method is used in engineering and hydraulics when you know the size of the pipe and the speed at which the water is traveling. It calculates the cross-sectional area of the pipe and multiplies it by the velocity.
Formula: $$Q = A \times v$$
- $A$: Cross-sectional Area of the pipe ($\pi \times r^2$)
- $v$: Velocity of the water
Common Flow Rate Units
Understanding the units is crucial for accurate conversion. Our calculator automatically converts between these common metrics:
| Unit | Abbreviation | Common Usage |
|---|---|---|
| Gallons Per Minute | GPM | US Plumbing, Showerheads, Garden Hoses |
| Liters Per Minute | LPM | Metric Plumbing, Fuel Pumps |
| Cubic Meters per Hour | m³/h | Industrial Pumps, Large Irrigation |
| Liters Per Second | L/s | Hydrology, Open Channel Flow |
Why is Flow Rate Important?
- Plumbing Efficiency: Ensuring your pipes are large enough to supply showers and appliances simultaneously without pressure drops.
- Irrigation: Calculating exactly how much water your lawn or crops receive to prevent over or under-watering.
- Pump Sizing: Selecting the correct pump horsepower to move specific volumes of water against gravity.