[1][2] Grans was the most effective defenceman of the IF Troja-Ljungby U16 Juniors in 2016–17, scoring 12 points.

At only 16 years old Grans played his first men's league match with the Malmö Redhawks in the Champions Hockey League (CHL) on 16 October 2018 against the EHC Red Bull München.

[3] Grans scored his first Swedish Hockey League (SHL) goal on 30 December 2019 against Brynäs IF.

On 4 June 2021, Grans was signed by the Los Angeles Kings to a three-year, entry-level contract.

[5] On 18 November 2024, Grans was called up from the Lehigh Valley Phantoms and made his NHL debut against the Colorado Avalanche.