Faucet Flow Rate Calculator
Calculates a faucet's flow rate in gallons per minute (GPM) by timing how long it takes to fill a known container. Use it to audit water consumption, compare fixtures, or check compliance with low-flow standards.
Last updated: October 2026
Flow Rate
2 GPM
Formula below · 2 sources (epa.gov, energy.gov) · Updated Oct 2026
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About this calculator
To find a faucet's flow rate, time how long it takes to fill a container of known size and scale it to one minute: a 1-gallon jug that fills in 30 seconds means 2.0 gallons per minute (GPM). The calculator divides the volume by the seconds and multiplies by 60.
How it compares
The U.S. federal maximum for bathroom faucets is 2.2 GPM at 60 psi. EPA WaterSense-labeled bathroom faucets and aerators use no more than 1.5 GPM at 60 psi, at least 30% less, and must still deliver at least 0.8 GPM at 20 psi so they work at low pressure. Showerheads are limited to 2.5 GPM federally and 2.0 GPM for the WaterSense label. See the table below.
Getting a good reading
Open the faucet fully, start the timer as the water enters the container and stop it when the water reaches the mark. Use the largest container you can handle: timing errors of a second matter less over 30 seconds than over 5. Repeat two or three times and average. Pressure varies through the day and when other fixtures are running, so test under normal conditions.
What the result means
A bathroom faucet well above 2.2 GPM likely has a missing or damaged aerator. A WaterSense-labeled aerator screws onto the spout, so you can cut the flow without replacing the faucet.
| Fixture | Federal maximum | EPA WaterSense label |
|---|---|---|
| Bathroom sink faucet | 2.2 GPM at 60 psi | 1.5 GPM at 60 psi (at least 0.8 GPM at 20 psi) |
| Showerhead | 2.5 GPM | 2.0 GPM |
How to use
Fill a container of known volume (in gallons) with the faucet fully open, time it in seconds, and enter both. The default, 1 gallon in 30 seconds, gives 2.0 GPM. A 1-gallon jug that fills in 24 seconds gives 2.5 GPM; a half-gallon that fills in 20 seconds gives 1.5 GPM, the WaterSense limit for bathroom faucets. For liters, enter the volume in gallons (1 liter = 0.264 gallons).
Frequently asked questions
How do I measure faucet flow rate at home?
Use the bucket test: open the faucet fully, time how long it takes to fill a container of known size, and divide the gallons by the seconds, then multiply by 60. Repeat a few times and average for a reliable figure.
What is a good faucet flow rate?
For bathroom faucets, 1.5 GPM or less meets the EPA WaterSense label, compared with the federal maximum of 2.2 GPM. Kitchen faucets usually flow more because they fill pots, and many have a pause or spray mode for washing.
Why does my flow rate change from test to test?
Flow rises with water pressure, which changes with the time of day, other fixtures running and the pressure regulator setting. WaterSense faucets are rated at 60 psi and must still give at least 0.8 GPM at 20 psi.
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Sources & references
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