With crowds of well-wishers and royal watchers set to descend on the Swedish capital the authority and with much of the city centre cordoned off for bus traffic, metro services are expected to be in high demand.
SL has now decided to increase services and remove ticket controls to help ease congestion.
"In practice you can travel for free," said SL CEO Göran Gunnarsson.
Gunnarsson was unable to project the anticipated revenue short fall from the move.
Extra staff are set to be employed to assist people to find their way through the metro system.
"There will be a lot of people coming from outside the city who do not know the system."