The MTA is increasing service on three subway lines — the 1, 7 and J — because riders are packing them, officials said yesterday.

The jammed 7 train got the biggest boost, with an additional 13 round trips every weekday.

The 1 train will have six more round trips during off-peak hours on weekdays.

And the J train will make three more round trips on Saturdays — its peak time for hipsters heading to and from Williamsburg’s shopping and bar scene.

The new schedules will begin in the summer, officials said.

The changes will cost the MTA an additional $2 million and are in addition to the $29 million in service investments the agency announced in July.