Could someone explain antenna dBi?

[Stas823]

Hello
I am looking to replace my ageing USB adapter with a pcie one, the one I had in mind has 3 changeable antenna and according to reviews they are weak. The antenna in question have 8dbi where as my current ones are 2dbi, will this mean it has x4 range?

Thanks

 

[bremen1874]

IIRC a 6dB increase will double the range (for the same input power).