It is one of the most common surnames in Sweden and has a number of alternative spellings.
Apart from Karlsson, Carlsson is the most common spelling variation.
The parallel Danish-Norwegian forms are Karlsen and Carlsen.
As of 2014, 92.3% of all known bearers of the surname Karlsson were residents of Sweden, 2.8% of Finland and 1.2% of Norway.
In Sweden, the frequency of the surname was higher than national average (1:52) in the following counties: In Finland, the frequency of the surname was higher than national average (1:945) in the following regions: