He played rugby union at Strathallan School and then for Dunfermline RFC.[1]
He was playing for Heriots at the time of his call up to the Edinburgh squad.
Professional career
He made his professional debut for Edinburgh Rugby in October 2016, as a substitute against Treviso.[1]
When Heriots joined the Super 6, he was drafted to his old club, playing against the Southern Knights on 7 December 2019,[2] and against Stirling County on 21 December 2019[3]
On 15 July 2021 it was announced that McCallum had signed a short term deal with Glasgow Warriors.[4]
It was announced on 25 November 2021 that McCallum had signed a contract with Worcester Warriors which will start on 1 January 2022.[6] The Worcester club went into administration after the 2022-23 season started; and their players were released.
He played for the Scotland Under 20s in the 2016 Rugby World Cup.[1]
In January 2018 he was called up to the senior Scotland squad for the 2018 Six Nations Championship.[10][11] He made his full senior debut from the bench, to play against Wales in the Six Nations.