Barber v. Thomas, 560 U.S. 474 (2010), is a United States Supreme Court case in which the Court held, 6–3, that prisoners incarcerated in federal prisons are entitled to up to 54 days of "good time credits" for every year they are incarcerated, allowing federal inmates to reduce their sentence by up to 54 days per year of imprisonment for exhibiting good behavior.

[2] The petitioner, Michael Barber, sought habeas corpus in a federal district court.

He argued that the Bureau of Prisons "inaccurately calculated his good time credit toward the service of his federal sentence."

Barber's petition was denied by the district court, on appeal the Ninth Circuit affirmed the ruling of the lower courts citing Tablada v. Daniels noting that the good time credit statute was ambiguous and the BOP's interpretation was reasonable.

Barber's attorneys argued that by allowing up to 54 days' credit for each year "of the prisoner's term of imprisonment," Congress intended federal sentences to be reduced by as much as 54 days for each year of the sentence imposed by the judge.