Gallons Per Minute Calculator (GPM)

Created by Rita Rain
Reviewed by Dominik Czernia, PhD and Jack Bowater
Last updated: Feb 02, 2023

Are you wondering how long it'll take to fill your bath? If so, our gallons per minute calculator can help you out. This water flow rate calculator includes multiple units and converts LPM to GPM, GPM to LPM, gallons per hour to gallons per minute, and much, much more.

Read the following text to find out more about the GPM meaning, GPM unit, and GPM formula. You will quickly learn how to calculate gallons per minute, for example, to determine how many GPM a shower uses!

🙋 If, on the other hand, you need to express a tank pressure into its equivalent volume flow rate in gallons per minute, our pounds per square inch to gallons per minute or PSI to GPM calculator is for you.

What is GPM?

GPM is a unit of the flow rate of liquids. "GPM" stands for "gallons per minute". The value of GPM is used to specify how fast water moves, e.g., through pumps, showerheads, and pipes. A gallon can be either the US liquid gallon (about 3.785 liters) or the British imperial gallon (4.546 liters).

How to use the GPM calculator

To find the flow rate - e.g., when you ask "How many gallons per minute does a shower use?", follow the points below:

  1. Choose the unit in which you will count the volume. For a myriad of other units of volume, you may find our separate volume calculator very interesting.

  2. Input the volume of the liquid in the first field.

  3. Choose the unit of time in which the given volume of water flowed.

  4. Input time of water flow.

  5. You'll find the flow rate in the last field of the gallons per minute calculator. You can change it to a different GPM unit as you please.

To find volume - e.g., know how much water you'll use for a 15-minute shower:

  1. Reset the water flow rate calculator using the arrow symbol below it.

  2. Input time and flow rate. The first field should be empty.

  3. You'll find the result in the "Volume" row.

To find time - e.g., how long it'll take to fill a pool:

  1. Enter the volume of a container in the first field of the GPM calculator.

  2. Enter the flow rate of water in the last field.

  3. Read the result in the second row.

In essence, all you need to do it enter any two variables you know and the GPM calculator will determine the third one. To calculate how many gallons per minute flows, we use the following GPM formula:

GPM = volume / time

Convert GPM to LPM and other units

What does GPM stand for? You should now know it. But did you know that our gallons per minute calculator includes various flow rate units, which enables quick conversion?

Let's say you want to change 15 GPM to LPM (gallons per minute to liters per minute). To do it, make sure the flow rate unit is set to gallons per minute and enter the number. Then change the unit to liters per minute. The GPM calculator will convert the number in the Flow rate field.

🔎 Learn more about gallons and how to convert them to other units of volume in our gallon calculator


How many GPM is a shower?

Standard showerheads have a water flow rate of around 2 GPM in the US. To count as water-saving showerheads, they need to have a maximum flow rate of 2 GPM. For older showers, the GPM may be higher.

How to calculate gallons per minute?

To calculate gallons per minute:

  1. Get a container (a bucket, for example) and keep a record of how many seconds it takes to fill the container with water.

  2. Convert the volume of water (bucket's capacity) to gallons.

  3. Divide the volume by the time expressed in seconds to get gallons per second.

  4. Multiply by 60 to get gallons per minute.

This is expressed with the following GPM formula:

GPM = volume / time

How many GPM is a garden hose?

The water flow rate from a garden hose typically ranges from 9 to 17 GPM (gallons per minute). Exact values depend on the type of hose. For example, the shorter the hose and the greater its diameter, the higher the flow rate. Another factor is the pressure in a water supply, which we measure in pounds per square inch (psi).

1 GPM equals how many LPM?

1 GPM equals circa 3.79 LPM, where GPM meaning is gallons per minute, and LPM means liters per minute. To convert US gallons to liters, multiply by 3.78541.

Rita Rain
US gal
Flow rate
US gal/min
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