Kallberg's family, on both his mother’s and father’s sides, played table tennis. This familial connection made it almost inevitable for him to try the sport. He enjoyed it from the start and recognised his talent early on. Despite trying other sports, he remained committed to table tennis.

Current Clubs and Coaches

Currently, Kallberg plays for Soderhamn UIF in Sweden and Borussia Dusseldorf in Germany. His coaching team includes Danny Heister from Borussia Dusseldorf and Jorgen Persson for the national team. These coaches have been instrumental in shaping his career.

Training Regime

Kallberg trains up to 25 hours a week. This rigorous training schedule helps him maintain peak physical condition and improve his skills. His dedication to training is evident in his performances.

Handedness and Personal Interests

Kallberg is right-handed. Outside of table tennis, he enjoys watching TV series. His favourite athlete is Swiss tennis player Roger Federer, who serves as an inspiration for him.

Sporting Philosophy and Famous Relatives

Kallberg lives by the motto "Just do it." His younger sister Christina has also made a name for herself in table tennis, representing Sweden at the world championships in 2017 and 2019.

Olympic Ambitions

Kallberg aims to win a medal at the Olympic Games. This ambition drives him to train hard and compete at the highest level. His selection for the singles event at the 2020 Tokyo Olympics was a significant milestone in his career.

Tokyo Singles Surprise

In May 2021, Swedish national team coach Jorgen Persson selected Kallberg for the singles event at the 2020 Tokyo Olympics. Despite being ranked fourth among Swedish players globally, Kallberg felt proud and committed to making the most of this opportunity.

"I feel very happy and proud and must take the opportunity," Kallberg said. "I will do everything I can to be in as good a shape as possible."