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Sensitivity Finder (PSA Method)

Move and try to stay on target as best as you can.

Tool to convert your DPI (Required):
https://www.mouse-sensitivity.com

-If you can use the "Universal Sensitivity Finder" from Aimlabs+
-If you can't, there are 2 free options:

https://slikts.github.io/sensfinder/ (The PSA method with no limit to how many steps you want to have)
https://www.reddit.com/r/GlobalOffensive/comments/43mto0/csgo_perfectsensitivity_finder/ (A portable version of the PSA method jar executable file)

Step one:
Convert your current sensitivity to be able to be used at 100 DPI.

Step two:
Change your current DPI to 100
(You do this so you have more values to work with, the lower the DPI, the more options you have as a sensitivity, thus allowing you to get a more precise final "perfect value")

Step three:
Get a sensitivity that allows you to make a full 360 from one corner of your mouse pad (do not apply this on pads that cover your entire desk)

Step four (Optional): 
If you want an even more precise value, repeat step three.

Step five:
Multiply your current sensitivity by 100 (your current DPI) to get your effective DPI and use it as your needed DPI. Then convert the current sensitivity to your effective DPI.