Most people sentenced to federal prison serve roughly 85 percent of the sentence the judge imposes. That figure is the practical answer to how much time you do in federal prison, and it holds because the federal system abolished parole for offenses committed on or after November 1, 1987. What shortens the gap between the number announced in court and the day someone walks out is a specific set of credits: time already spent in custody, good conduct time, First Step Act earned time credits, and a handful of program-based reductions.
Why There Is No Parole to Cut Time Further
The Sentencing Reform Act of 1984 eliminated federal parole for anyone whose offense occurred on or after November 1, 1987. Before that change, defendants typically served only about 58 percent of their imposed sentence, with release largely set by the United States Parole Commission.1United States Sentencing Commission. Fifteen Years of Guidelines Sentencing – Executive Summary Congress wanted truth in sentencing, and abolishing parole accomplished that.
The Parole Commission still exists, but its jurisdiction is limited to offenses committed before November 1, 1987, certain D.C. Code offenders, and a few other narrow categories.2Department of Justice. United States Parole Commission Organization, Mission and Functions Manual For essentially every person entering federal prison today, there is no parole board waiting to grant early release. The sentence you receive is the sentence you serve, minus the credits described below.
Good Conduct Time: The Main Driver of the 85 Percent Figure
Good conduct time is the largest single reduction most federal prisoners will see. Under 18 U.S.C. § 3624(b), a federal prisoner serving more than one year can earn up to 54 days of credit for each year of the sentence imposed, provided the Bureau of Prisons determines the prisoner displayed exemplary compliance with institutional rules that year.3Office of the Law Revision Counsel. 18 U.S. Code 3624 – Release of a Prisoner
That 54-days-per-year figure is what produces the well-known 85 percent rule. Before the First Step Act of 2018, a disputed calculation method capped the effective credit at roughly 47 days per year. The First Step Act fixed this by tying the credit to the sentence imposed rather than to time actually served, bringing the real-world credit up to the full 54 days Congress originally intended.4Federal Register. Good Conduct Time Credit Under the First Step Act
The math on a ten-year (120-month) sentence: 54 days multiplied by 10 years equals 540 days, or about 18 months. Subtract that from 120 months and you get roughly 102 months of actual incarceration, just under eight and a half years. That tracks almost exactly to the 85 percent benchmark.5Federal Bureau of Prisons. An Overview of the First Step Act
How Good Conduct Time Gets Taken Away
Good conduct time is not automatic. The Bureau of Prisons classifies rule violations into four severity levels, and losing good time credit is a mandatory sanction at the higher levels. A single greatest-severity violation, such as assault on staff, murder, or rioting, costs at least 41 days of credit. High-severity violations carry a mandatory loss of at least 27 days.6eCFR. 28 CFR Part 541 Subpart A – Inmate Discipline Program Moderate and low-severity violations can also cost credit, though usually only after repeat offenses in the same year.
Once credit is lost, it cannot be restored later. A single serious incident can add months to how long someone actually stays in prison.
Credit for Time Already Served Before Sentencing
Many federal defendants spend months or years in custody before their case is resolved. Under 18 U.S.C. § 3585(b), a defendant gets credit toward the sentence for any time spent in official detention as a result of the offense that led to the sentence, or as a result of any other charge arising from the same arrest, as long as that time has not already been credited against a different sentence.7Office of the Law Revision Counsel. 18 U.S. Code 3585 – Calculation of a Term of Imprisonment
Someone arrested in a federal drug case who sits in a county jail for 14 months awaiting trial and sentencing gets those 14 months subtracted from the prison term. The Bureau of Prisons calculates this credit, not the judge, and disputes over how it is applied are common. If pretrial time straddles both federal and state charges, the accounting gets complicated quickly.
First Step Act Time Credits
Separate from good conduct time, the First Step Act created a second category of earned time credits tied to participation in rehabilitative programming. Eligible prisoners earn 10 days of time credits for every 30 days of successful participation in approved recidivism reduction programs or productive activities. Prisoners classified as minimum or low risk for reoffending, who have maintained that classification over two consecutive assessments, earn an additional 5 days, for a total of 15 days per 30-day period.8Office of the Law Revision Counsel. 18 U.S. Code 3632 – Development of Risk and Needs Assessment System
These credits work differently from good conduct time. Instead of shortening the overall sentence, FSA time credits are applied toward earlier transfer into prerelease custody, meaning a halfway house (residential reentry center) or home confinement, or toward early placement on supervised release.9eCFR. 28 CFR Part 523 Subpart E – First Step Act Time Credits Someone who stacks up enough FSA credits could spend the last several months of the sentence living at home under electronic monitoring rather than inside a prison facility.
Who Cannot Earn FSA Time Credits
The statute lists dozens of disqualifying offenses. They tend to fall into predictable categories: violent crimes, terrorism, espionage, sex offenses, human trafficking, and high-level drug offenses. Repeat felons convicted of firearm possession are also excluded.5Federal Bureau of Prisons. An Overview of the First Step Act Prisoners with a final order of removal under immigration law can earn the credits but cannot apply them toward early release.8Office of the Law Revision Counsel. 18 U.S. Code 3632 – Development of Risk and Needs Assessment System
The full list of disqualifying convictions is extensive and includes offenses you might not immediately think of, such as certain immigration crimes, destruction of aircraft, and fraud involving computers when national security information is involved.10Federal Bureau of Prisons. Disqualifying Offenses Inmates who are disqualified can still participate in programming and earn other benefits, but the early-release pathway is closed.
Up to a Year Off Through RDAP
The Residential Drug Abuse Program, or RDAP, is one of the most sought-after programs in the federal system because completing it can shave up to 12 months off a sentence, a reduction separate from both good conduct time and FSA time credits. Under 18 U.S.C. § 3621(e), the Bureau of Prisons may reduce a nonviolent offender’s sentence by up to one year if the prisoner successfully finishes the residential substance abuse treatment program.11Office of the Law Revision Counsel. 18 USC 3621 – Imprisonment of a Convicted Person
Eligibility requires a documented substance use disorder, a conviction for a nonviolent offense, and completion of all three phases: the in-unit residential treatment (typically nine months), follow-up programming in the general population, and transitional treatment at a halfway house or on home confinement. The size of the reduction depends on sentence length:
- 30 months or less: up to 6 months off
- 31 to 36 months: up to 9 months off
- 37 months or more: up to 12 months off
Prisoners with prior convictions for certain violent crimes, including homicide, robbery, aggravated assault, arson, kidnapping, and sex offenses involving minors, are excluded regardless of the current offense.12Federal Bureau of Prisons. Early Release Procedures Under 18 USC 3621(e) RDAP has a waiting list at most facilities, so it pays to ask about enrollment early.
Compassionate Release for Extraordinary Circumstances
Federal courts generally cannot modify a sentence after it is imposed, but compassionate release is the major exception. Under 18 U.S.C. § 3582(c)(1)(A), a court can reduce a sentence if it finds extraordinary and compelling reasons warrant the reduction. Before the First Step Act, only the Bureau of Prisons could file such a motion. Now, a prisoner can go directly to court after exhausting administrative remedies or waiting 30 days from the date the warden receives the request, whichever comes first.13Office of the Law Revision Counsel. 18 USC 3582 – Imposition of a Sentence of Imprisonment
The qualifying categories are narrow:
- Terminal illness with a life expectancy of 18 months or less.
- A progressive illness or injury leaving the prisoner completely disabled or confined to a bed or chair more than half of waking hours.
- Elderly prisoners aged 70 or older who have served at least 30 years, or those aged 65 or older who have served at least 50 percent of their sentence and suffer from serious health conditions related to aging.
- Family emergencies involving the death or incapacitation of the caregiver for a prisoner’s minor child, or the incapacitation of a spouse or partner when the prisoner is the only available caregiver.
Even when a case meets one of these categories, the judge must still weigh the sentencing factors under § 3553(a), so a strong medical case can still be denied if the court considers the prisoner a danger to the public.14Federal Bureau of Prisons. Procedures for Implementation of 18 USC 3582 and 4205(g)
Putting the Numbers Together
Take a 120-month sentence as a working example. If the defendant spent 6 months in pretrial detention, § 3585(b) credit knocks the balance down to 114 months. Maximum good conduct time of 54 days per year takes roughly 18 months off, bringing actual incarceration down to about 96 months. Someone who qualifies for and earns FSA time credits at the maximum rate could transition to a halfway house or home confinement several months before that date. Completing RDAP could take another 12 months off.
The 85 percent rule is a fair shorthand for most cases. People who stack multiple credits and reductions can end up serving substantially less, closer to 75 percent of the imposed sentence in the best-case scenario. Someone who picks up serious disciplinary infractions and loses good conduct time can serve closer to 100 percent. The federal system rewards compliance and program participation in ways that make a real, measurable difference in how long someone actually stays locked up.
Release Is Not the End of the Sentence
Getting out of prison does not mean the sentence is over. Nearly every federal sentence includes a term of supervised release that begins the day the prisoner walks out. It is set by the judge at sentencing rather than by a parole board later.
Maximum terms of supervised release depend on the severity of the conviction:
- Class A or B felony: up to 5 years
- Class C or D felony: up to 3 years
- Class E felony or misdemeanor: up to 1 year
Certain offenses, including terrorism, sex crimes involving children, and some other categories, carry supervised release terms of up to life.15Office of the Law Revision Counsel. 18 USC 3583 – Inclusion of a Term of Supervised Release After Imprisonment
Standard conditions include no new criminal conduct, no illegal drug use, mandatory drug testing within 15 days of release and periodically after, and payment of any court-ordered restitution. A federal probation officer supervises compliance and can petition the court to revoke supervised release for violations, which sends the person back to prison. A revocation can add significant additional incarceration, sometimes years, on top of the time already served.