Journal impact factor is the way journals are measured in terms of quality and are a good way to select a journal to publish in. Impact factor measures the number of citations a journal has had over the previous year. It is calculated using the formula:
Number of citations received in 2019 by items published in the journal in 2017-2018
divided by
Number of citable items published in the journal in 2014-2015
In essence it measures the amount of citation the items in the journal have had during the current year in order to showcase the quality of the journal.
You can use the tools below to calculate journal impact factor.
However journal impact factor is not a completely comprehensive measure and can be skewed - see video below.
So remember to do in-depth research into each journal to which you are thinking of submitting work.