Del Hampson, 21, unemployed, attacked Sarah Burke, the oldest resident of the home in Redruth, Cornwall, during a burglary on 19 December last year.
Francis Gilbert, for the prosecution, told Truro Crown Court that Mrs Burke's cheekbone was broken in two places, her lower jaw fractured in three places and her upper jaw broken away from her skull. Marks on her head suggested that she had been stamped on as she lay in bed during a 'fierce attack'.
Mrs Burke, who was 4ft 6ins tall and six-and-a-half stone, died of shock in hospital three days later, less than a month before her 100th birthday.
Hampson, of Penventon Terrace, Redruth, had denied murder, but the prosecution rejected his plea of manslaughter.
Mr Justice Mantell told him the offence was 'cowardly, contemptible and wicked'.
The court was told that Hampson, who had spent the afternoon and evening drinking, attacked Mrs Burke late at night after breaking in through a window. Then, 'covered' in blood, he went to his girlfriend's home.
His clothes were washed - but blood of the same type as Mrs Burke's was found on his neck-chain and on furniture at his girlfriend's home. After his arrest he told police that he had hit Mrs Burke a couple of times with his fist, but had not intended to kill or seriously injure her.
Hampson was also jailed for three years for burglary and 64 other admitted offences.
Cornwall County Council said yesterday it is to spend more than pounds 300,000 on improved security at its 30 residential homes. It also announced that two women night-care assistants who had been on duty on the night of the attack had been dismissed after an independent inquiry found they had failed to check on Mrs Burke at midnight or 3am and had misled police about when checks were made.