Flow units converter

Convert cfm to m3/h, gpm to l/s, cfm to cmh …

 24 August 2019


UnitConversion.org – the universal assistant for all of your unit conversion needs.

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How to use the Flow Units Converter

  1. Select the unit you want to convert from in the input unit list on the left.
  2. Select the unit you want to convert to in the output unit list on the right.
  3. Enter the value of the input unit to convert from in the input box on the left.
  4. The tool will immediately display the equivalent value of the output unit in the output box on the right.

Steps 1 to 3 may be executed in random order.

The value of your input unit can be converted to any other unit by just selecting a different output unit in the list on the right.

Definition of flow rate

Flow rate (Q) is defined to be the volume (V) of fluid passing through a cross-sectional area (A) during a period of time (t).

With a formula, this can be written as:

Q = V t

The basic unit for flow rate in the metric system is m3/s (SI unit).

However, this is a very large unit, causing the quantity for small flow rates to be a very small number starting with a zero and followed by multiple zeros after the decimal point. Since this is not practical, often use is made of derived units of the SI system. These are, for example, m3/h, and l/h or l/min.

How to calculate flow rate?

Let’s take the example of a liquid flowing through a uniform pipe with a cross-sectional area A.

flow rate calculation in a pipe

The liquid is flowing from left to right through the pipe.

Time t0 is the point where we start the measurement and time t1 is the endpoint of the measurement.

During the time interval t1 – t0, a certain volume of liquid has passed through the cross sectional area A. This volume can be calculated as follows:

V = A x d

where d = the distance travelled by the liquid during time interval t1 – t0

The flow rate through the pipe will then be:

Q = V t = A x d t1 – t0

The average flow velocity through the pipe is:

vav = d t1 – t0

So, if you only know the cross-sectional area and the speed at which the liquid is moving through the pipe, you can use an alternative formula to calculate the flow rate:

Q = A x vav

Interpretation of flow rate units

A flow can be considered as fluid in motion, moving from one place to another in a steady stream.

The descriptions of some units below are written in such a way that you can get an idea of what this unit means. Other, similar units can easily be derived from this description by simply replacing a few words in the sentence (e.g., hour replaced by minute or yard replaced by foot).

Cubic meter per second – The quantity of liquid equivalent to a flow, one meter wide by one meter deep, flowing with a velocity of one meter per second.

Liter per hour – The amount of liquid equivalent to a flow that fills a volume of one liter every hour.

Gallon per hour – The amount of liquid equivalent to a flow that fills one gallon every hour.

Acre-foot per hour – The volume of liquid, covering one acre one foot deep, which moves from one place to another in one hour.

Cubic yard per hour – The quantity of liquid equivalent to a flow, one yard wide by one yard deep, flowing with a velocity of one yard per hour.

Conversion factors Imperial/Customary to Metric

The following tables are showing the conversion factors from the Imperial and US Customary system to the Metric system.

swipe or scroll
 CONVERT TO (multiply by)
CONVERT FROMm3/sm3/minm3/hcm3/scm3/mincm3/hL/sL/minL/h

Some factors are slightly rounded compared to the factors used in the Flow Units Converter.

 CONVERT TO (multiply by)
CONVERT FROMm3/sm3/minm3/hcm3/scm3/mincm3/hL/sL/minL/h

Some factors are slightly rounded compared to the factors used in the Flow Units Converter.

 CONVERT TO (multiply by)
CONVERT FROMm3/sm3/minm3/hcm3/scm3/mincm3/hL/sL/minL/h

Some factors are slightly rounded compared to the factors used in the Flow Units Converter.

Example of conversion

Conversion from US Customary gal(US)/s to Metric m3/s:

5 gal(US)/s = 5 x 0.003785 m3/s = 0.018925 m3/s

If you perform this conversion directly in the converter, you will see that the sixth digit after the decimal point is different. This is because the conversion factors in the tables are rounded. The converter is more accurate.

Conversion factors Metric to Imperial/Customary

The following table is showing the conversion factors from the Metric system to the Imperial and US Customary system.

swipe or scroll
 CONVERT TO (multiply by)
CONVERT FROMgal(US)/sgal(US)/mingal(US)/hgal(UK)/sgal(UK)/mingal(UK)/hbbl(US)/sbbl(US)/minbbl(US)/hbbl(US)/dac*ft/hhcf/minhcf/hoz/soz/minoz/hoz(UK)/soz(UK)/minoz(UK)/hyd3/syd3/minyd3/hft3/sft3/minft3/hin3/sin3/minin3/h

Some factors are slightly rounded compared to the factors used in the Flow Units Converter.

Example of conversion

Conversion from Metric m3/s to US Customary gal(US)/s:

3 m3/s = 3 x 264.1720 gal(US)/s = 792.516 gal(US)/s


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