Liters per Minute Calculator
Table of contents
What are liters per minute?How to use the liters per minute calculatorHow to calculate liters per minute: Flow rate calculation from crosssectional areaFAQsThe liters per minute calculator allows you to calculate the flow rate in your pipe in liters per minute (L/min), either from the volume of liquid and time taken or from the crosssectional area and velocity of the liquid. In this article, we will see:
 What are liters per minute?
 How to calculate liters per minute using the liters per minute calculator.
 How to convert liters per minute to GPM (gallons per minute) or CFM (cubic feet per minute).
 How much water can flow through a 6inch pipe?
 How to calculate the flow rate through a pipe?
Visit our flow rate calculator for a more advanced tool for calculating flow rate. It also allows you to compute calculations in liters per minute.
What are liters per minute?
The liter per minute (LPM or L/min) is a unit that expresses flow rate. As its name suggests, it tells you how many liters flow through your tap or a pipe in one minute. This is useful when you want to calculate how much water you consume while taking a shower or during other daily activities.
The liters per minute should not be confused with the standard liters per minute (SLPM or SLM), as this is a unit of the flow rate of gases, not liquids!
How to use the liters per minute calculator
The primary function of the liters per minute calculator is to determine the flow rate in your pipes from volume and time taken, which is the first section of the tool.

Let the liquid flow for a measured amount of time and determine the volume of the collected liquid.

Insert the volume and the time in the liters per minute calculator.

In no time, you will see the flow rate of your tap in liters per minute! Remember that you can always convert the units as you please, for example, from liters per minute to GPM (gallons per minute). All you have to do is click on the unit and choose.
If you want to do this calculation manually, divide the volume in liters by the time in minutes, and you'll instantly know the flow rate in liters per minute. How easy is that?
How to calculate liters per minute: Flow rate calculation from crosssectional area
The other sections of this tool allow you to calculate the flow rate in liters per minute from the crosssectional area and velocity.
If you don't know the crosssectional area of your tube:

Expand the
Crosssectional area calculation
section. 
Choose the shape of the crosssection of your tube. In the case of a circular crosssection, you can also select whether the tube is full or not.

Let's say we want to calculate the flow rate through a circular tube. We pick
Circle
and insert ourInternal diameter
, for example, 3 in. 
The liters per minute calculator will tell you the size of the crosssectional area: 7.07 in^{2}.
If you think about it, the crosssectional area of a circular tube is nothing other than the area of the circle with a diameter equal to the internal diameter of your tube. Therefore, we can calculate it as follows:
area = (internal diameter² × π) / 4 = ((3 in)² × π) / 4 = 7.07 in²
Now, let's see how to calculate liters per minute (volumetric flow rate) using this calculator. If you have calculated the crosssection using our tool, it will be automatically displayed in the Volumetric flow rate
section. Otherwise, you will have to insert it yourself.

Insert or doublecheck the crosssectional area. In this case, we will leave our calculated result.

Insert the velocity of the liquid. Let's say this liquid flows at 3 ft/sec.

The volumetric flow rate is 250.25 liters per minute (L/min). This is given by the following equation:
volumetric flow rate = crosssectional area × velocity
If you are performing the calculation by yourself, make sure the units of your data are coherent. For example, if you want to calculate the volumetric flow rate in liters per minute, the crosssectional area must be expressed in dm^{2}, and the velocity in dm/min. (1 liter = 1 dm^{3})
Look at the FAQ section below to learn how to convert between GPM and L/min, as well as between CFM and L/min.
How do I convert 3 liters per minute to GPM?
To convert liters per minute to GPM, you will need to divide the value by 3.785. For example, if you want to convert 3 LPM to gallons per minute, you have to do the following calculation:
3 LPM / 3.785 = 0.793 GPM
If you want to convert GPM to L/min, you must multiply by 3.785 instead of dividing.
How do I convert liters per minute to CFM?
To convert liters per minute into CFM (cubic feet per minute), you have to divide the value by 28.317. If you want to convert CFM into L/min, you will need to multiply by 28.317. For example, let's convert 50 liters per minute to CFM:
50 LPM / 28.317 = 1.766 CFM
How much water can flow through a 6inch pipe?
To calculate how much water can flow through a 6inch pipe, follow these steps:

Calculate the crosssectional area of your pipe. If, for example, your pipe is circular, its crosssectional area is equal to 28.274 in^{2} (area of a circle with a diameter 6 in).

Determine the velocity of the flow. Let's assume that the velocity of our liquid is equal to 20 in/s.

To calculate the flow rate in liters per minute, convert the velocity to dm/min (20 in/s = 304.8 dm/min), and the crosssectional area to dm^{2} (28.274 in^{2} = 1.824 dm^{2}).

Use the following formula:
volumetric flow rate = crosssectional area × velocity
Now you know that the volumetric flow rate of water flowing through a 6inch pipe is equal to approximately 555.955 liters per minute. For more precision, you can use Omni's liters per minute calculator.
How do I calculate flow rate through a pipe?
Follow these simple steps to calculate the flow rate through a pipe from volume and time taken:

Let the liquid flow for a determined amount of time.

Measure the volume of the collected liquid.

If you want to calculate the flow rate in liters per minute, convert the volume to dm^{3}, and the time, to minutes. If the volume is expressed in gallons and the time in seconds, your flow rate will be expressed in gallons per second.

Divide the volume by the time. This is your flow rate!