The Ministry of Justice says the total prison population in England and Wales has reached more than 86,000, just 1,500 inmates below capacity.
Prison officials are considering emergency plans to create space for the extra inmates.
Prime Minister David Cameron says judges have acted correctly in imposing tough sentences for the rioters.
Among the most criticized sentences, are four-year jail terms given to two men for attempting to incite rioting by posting messages on Facebook.
Activists and high-profile attorneys have criticized the harsh punishments and expect more successful appeals.
Meanwhile, Prince William and his wife Kate, also known as Catherine, Duchess of Cambridge, visited a community center in Birmingham, England, where three people were killed in a hit-and-run crash during the violence. The victims were hit by a car as they protected stores from looters.
The couple also met with families of the victims and greeted emergency workers at the center.
The Associated Press contributed to this report.