Our GPM calculator will compute the gallons of water flow per minute. You can also use our GPM formula for manual calculations.
Enter the volume of water in gallons and the time taken to fill that volume to calculate the flow rate in GPM (gallons per minute):
GPM stands for gallons per minute – a calculation for the volumetric flow rate of water. You can use the GPM calculator to determine the water flow rate for a bathtub, showerhead, garden hose, or sink. For this calculator to work, you’ll need to fill a gallon container with water, noting how many seconds it takes.
Note: Use this calculator for US gallons – the equivalent of 128 fluid ounces. The Imperial gallon is a bit larger, at 153.72 US fluid ounces.
GPM = 60/number of seconds to fill one gallon of water
An Example of Calculating Gallons Per Minute
If you’d like to find the GPM of your bathtub nozzle, fill a one-gallon container with water and time how long it takes. Then divide 60 by your timed results. For example, if it took five seconds, you’d divide 60 by 5 for a result of 12 gallons per minute.
12 gallons per minute = 60/5 gallons per second
How to Convert Gallons Per Minute to Other Volumetric Flow Rates
Convert your GPM to LPM (liters per minute) or GPH (gallons per hour) with these simple equations.
One gallon is equal to 3.78541 liters. To convert GPM to LPM, multiply by 3.78541. The LPM signifies the number of liters of water flow per minute.
LPM = GPM x 3.78541
The GPH or gallon per hour indicates the number of gallons of water flow in a single hour – an important metric when determining how long it will take to fill a pool or large tank.
To convert from GPM to GPH, multiply by 60, which is the number of minutes in one hour.
GPH = GPM x 60
For example, if your water hose delivers 12 gallons per minute, multiply that by 60 for 720 gallons per hour.
Frequently Asked Questions (FAQ)FAQ
What’s the average GPM for a water hose?
A standard garden hose has a water flow rate of 9 to 17 gallons per minute. While this is a broad average, the type of hose and water pressure influences the GPM.
What’s the average GPM for a showerhead?
A standard showerhead has a GPM of 2.5. Low-flow showerheads must have a GPM of less than two, with 1.8 being the average.
What’s the average GPM for a sink faucet?
Due to federal regulations, a sink faucet must not have a GPM flow rate of more than 2.2. Average GPMs for household sink faucets range from 1.0 to 2.2.