Bernard Ampaw, 19, appeared for sentence at Chelmsford Crown after a jury found him guilty of murder and robbery last month
His victim, Francis Nsiangangu, 31, known locally as Casper, was stabbed at least two times and slashed twice on his arms when he was attacked at Tower Hill, on Saturday September 27.
A seven-week trial at heard that Casper was actively involved in the supply of cannabis.
Clive Mundoma, 19, a student, formerly of High Street, Brentwood, who was also found guilty of robbing Casper was jailed for six years.
Ampaw of Wombridge Road, Telford, was told by Judge Gratwicke: "You were convicted of robbery and murder for the savage killing of Francis Nsiangangu during which you viciously and cold bloodedly stabbed him twice, one of which penetrated his heart.
"It was you who plunged that knife into him on at least two occasions following which you run off with Mundoma carrying the rucksack you had stolen."
The judge told Mundoma: "The fact remains it was you who decided to rob Casper and in so doing encouraged Ampaw to engage in the attack by saying 'lets nank (rob) him'. It was you who first used violence upon Casper by pulling his rucksack from him."
The trial had heard how the attackers had contacted Casper to arrange to buy cannabis.
But when they met at Tower Hill they ordered Casper to hand over his drugs and cash. When refused and tried to get away he was stabbed.
As the attackers ran off with Casper's rucksack, which contained cannabis, he staggered away and banged on the door of a barber's shop, calling for help.
Members of the public rushed to help him but he collapsed and died on the pavement.
The attackers left the area in a taxi they had pre-booked and asked to wait while they met Casper.
They were arrested following a lengthy investigation by Essex detectives who used computer, CCTV and telephone technology to track their movements before and after the killing. They also found in the taxi a library membership card that Casper held to use a computer at Brentwood library.
Det Supt Mark Hall, who led the investigation said after the hearing: "The evidence clearly showed that the defendants had planned to meet Casper in a quiet residential area with the intention of purchasing cannabis from him.
"They made arrangements by booking a cab in advance and asked the driver to wait whilst they met Casper.
"A disagreement ensued between the parties and when Casper tried to fight back he was subjected to extreme violence which led to his death. One lunge of the knife penetrated through his clothes and into his heart.
"The assailants then travelled by taxi to east London, acting as if they had hardly a care in the world, preferring to chat about the evening's football match.
"They then went their separate ways and Ampaw made himself scarce by going to Wolverhampton.
"But he was found thanks to the use of computer and phone technology and excellent detective work.
"The attack was unprovoked and has cost a young man his life. This case demonstrates the tragic consequences of knife crime. Casper's unnecessary death has impacted on his many friends and has devastated his family.
"I would like to thank those who came forward with information, which enabled police to obtain these convictions. Our sympathies are with Casper's family and we hope that the sentences today will bring a small degree of closure to their grief."