The federal prison system held 154,932 people as of September 27, 2025, and 61 percent of the analyzed population had been convicted of an offense carrying a mandatory minimum penalty, according to the United States Sentencing Commission.
Of the total in Federal Bureau of Prisons custody, 134,850 were serving a sentence for a federal conviction. The Commission matched its records to 132,371 of them for the detailed analysis. Another 20,082 people were awaiting trial or had been sentenced in District of Columbia or military courts.
The population largely reflects recent federal sentencing. Sixty-nine percent had been sentenced within the previous five years and 89 percent within the previous decade. The average age was 42; 24 percent were at least 50 and 8 percent were 60 or older.
Sentences were lengthy on average. The mean guideline minimum was 173 months, while the mean term actually imposed was 153 months. Ninety-eight percent also received a period of supervision to follow prison, placing most releases under continuing court-ordered conditions.
Mandatory minimum statutes applied to 61 percent of the analyzed group. Of those people, 20 percent were relieved from the penalty. Relief can arise through legal mechanisms that permit a sentence below the statutory floor, but the fact sheet does not reduce that mix to one single pathway.
Weapons also appeared frequently in the records: 32 percent were serving a sentence for an offense involving a weapon. That category combines convictions under 18 U.S.C. Section 924(c), guideline weapon enhancements and cases involving both, so it should not be read as one uniform offense.
The Commission reported that 91 percent pleaded guilty and 98 percent of sentences were imposed after the Supreme Court’s Booker decision made the federal guidelines advisory rather than mandatory. Forty-five percent were sentenced within the guideline range, while other cases involved departures or variances.
These statistics describe people present in custody on a single date, which emphasizes longer sentences more than a count of annual admissions would. They also exclude incomplete sentencing records from some calculations and cannot show how quickly the population is changing.
Even with those limits, the snapshot is a detailed scale check: more than 150,000 people were in federal custody, most had entered under sentences imposed within the past decade, and mandatory-minimum statutes shaped the legal exposure of a clear majority of the analyzed prison population.