Waitakere District Court heard how on the evening of March 20 he began a heavy boozing session at The Hangar bar in Henderson.
More than four hours later Brampton got behind the wheel.
Only minutes into the journey back to his Massey home he hit Mr Caldwell from behind, throwing him onto the car's windscreen and over the roof.
The cyclist - who was wearing a helmet and had a flashing rear light on his bike - slid along the road before smashing into a parked car.
Judge Glubb listed the horrendous effects: "significant injuries to the chest cavity, numerous broken ribs, a broken humerus, a severed right leg above the ankle and internal decapitation".
Mr Caldwell's wife Astrid spoke of the impact of the "horrific accident" on her and their teenage son.
"I remember every detail; a memory that keeps coming back, a sense of dread and loss," she said through tears.
"The hardest of all is knowing we'll never be able to physically touch him and hold him."
When police arrived at Brampton's home, a couple of hours after the incident, they found him in bed with the car keys in his pocket.
He refused to accompany them to the station, swore at them and eventually lashed out officers as they tried to restrain him.
"It took three to bring you under control," Judge Glubb said.
When he was eventually processed - three hours after the crash - he gave a reading of 160 milligrams of alcohol per 100 millilitres of blood.
The legal limit is 50.
His lawyer Graeme Minchin said he did not remember anything about the incident, which could have been the result of concussion from the crash.
Mr Minchin said Brampton was "deeply ashamed" of his actions and afterwards had enrolled on an alcohol-addiction programme.
The court heard he was later kicked off the course for using cannabis.
The judge called it a "tragic and utterly-avoidable death".
"You chose to get into that car and drive and an innocent man is dead as a consequence. It's disturbing to the court and the community that despite all the road-safety messages, all the campaign, individuals like you still choose to drive when heavily affected by alcohol," he said.
"It must stop."
Brampton was also disqualified from driving indefinitely.