In this world map, you can check at a single glance which countries have more people with the surname Janczak. As you can see, it's effortless to notice which countries have a higher number of people carrying the Janczak surname.
The quantity of people with the surname Janczak that we can find in each country can help us discern the origin of the surname Janczak, as logic tells us that the place with the most people surnamed Janczak will be the country or area of origin of the surname Janczak.