Bell, 29, was in the final year of his three-year, $9.3 million contract that included $4.3 million guaranteed. He was set to make a base salary of $2.5 million for the 2016 season.
According to OverTheCap.com, releasing Bell will free up $2.5 million in available cap space while creating $1 million in dead money.
In 2015, Bell appeared in 13 games for the Lions and ran for 311 yards on 90 carries (3.5 YPC) to go along with 22 receptions for 286 yards receiving and four total touchdowns. Pro Football Focus has him rated as the No. 27 running back out of 68 qualifying players.