Gallons per minute, abbreviated as GPM, is a unit of volume flow rate. GPM is used to describe how much water is flowing through a certain cross-sectional area, for example a pipe or a shower head. GPM is often measured by using a pressure tank or pitot tube and it can be useful when trying to understand the performance of a pump, for instance by determining its flow rate at a given Head measurement.
When measuring a GPM, it is best to use a container that you know the capacity of. This will allow you to make a more accurate calculation. You can use a stopwatch or a timer to record how long it takes for the container to fill. For the most precise reading you should measure this several times and average the results. Once you have recorded the number of seconds it took to fill the container you can then calculate your GPM by dividing this by 60. For example if it takes 14 seconds for the container to fill you will get 5 divided by 60 which gives a result of 21.4 GPM.
If you are using a GPM calculator online, first check that the flow rate unit is set to gallons per minute before entering a number. Once you have done this, simply change the unit to liters per minute and the calculator will automatically convert it for you. This unit converter also works in reverse; you can enter a number of liters and the calculator will convert it for you to gallons per minute. gpm to lpm converter