Surname Sumlak (Sumlak 
) , in the entire world, is a very rare family name. The family name Sumlak is characteristic of Canada, where it is a very rare surname, Switzerland, and New Zealand. Not in comparison with a country's population, it is the most numerous in Canada, Germany, and Switzerland. Very seldom, Sumlak is the forename as well as the last name.
| VARIANT | COUNTRY |
|---|---|
| Sumlak | Germany, Canada, Thailand, Switzerland, India |