28-year-old Jaynesh Chudasma was driving more than two and a half times over the alcohol limit, The Guardian reported.
The accident occurred on 26 January at about 8.40 pm when a group of boys was walking to a birthday party.
Chudasma, who worked as a car hire worker, lost control of his car while attempting to overtake another vehicle. His Audi struck the boys head on.
Harry Rice (17), George Wilkinson (16) and Josh Mcguinness (16) died at the scene.
Chudasma and his co-passenger got out of the car and tried to run away, but the friends of the victims caught Chudasma.
Police traced alcohol and traces of cannabis in the driver's system.
He pleaded guilty to causing deaths by dangerous driving during a hearing at the Old Bailey in London.
The court will pronounce the sentence on the next hearing, on March 9.
