Flow Rate Calculator
Calculate water flow rate from a measured volume and time, or from the cross-sectional area and average flow velocity. Results are shown in common US and metric units.
Choose a calculation method and enter your measurements. Results update automatically as you change the inputs or units.
Measured volume
Flow cross-section
YOUR ESTIMATE
Volumetric Flow Rate
Flow rate10 US gal/minBased on 5 US gallons collected in 30 seconds.
Gallons per hour600 US gal/h
Liters per minute37.854 L/min
Cubic meters per hour2.271 m³/h
These are volumetric flow rates, not pressure or stored pipe capacity.
How to Use the Calculator
- Select Volume and time to use a measured amount of water, or Cross-sectional area and velocity when those values are known.
- Enter each measurement and choose its unit from the dropdown.
- Read the automatically updated flow rate in US gallons per minute, US gallons per hour, liters per minute, and cubic meters per hour.
- Use Reset Calculator to restore the default example values.
Assumptions and Limitations
The volume-and-time method assumes the collected volume and elapsed time are measured accurately. The area-and-velocity method uses the flow cross-sectional area and average velocity. The calculator estimates volumetric flow rate only; it does not predict household water pressure, pipe friction losses, or actual system performance. Results are rounded for readability.
