Federal Sentence Computation: Jail Credit, Good Time and Release Dates

Sentence computation is how the Federal Bureau of Prisons (BOP) turns a federal judge's sentence into a release date. The BOP decides when the sentence started, subtracts credit for time already spent in custody before that date (often called jail credit), and then subtracts good conduct time. First Step Act time credits can move part of what is left out of prison.

This guide explains each step in plain words, works through an example, shows how to look up a projected release date, and explains what to do if the BOP gets it wrong. It is not a calculator. The BOP's own computation is what counts, and its rules are in Program Statement 5880.28, Sentence Computation Manual (CCCA of 1984). A program statement is the BOP's written policy for its staff.

When does a federal sentence start?

A federal prison sentence starts on the date the person "is received in custody awaiting transportation to, or arrives voluntarily to commence service of sentence at, the official detention facility at which the sentence is to be served" (18 U.S.C. § 3585(a)).

In practice, under the BOP's manual (PS 5880.28, ch. 1):

• Already in federal custody at sentencing. If the person is in federal custody on this case and serving no other federal sentence, the sentence usually starts on the day it is imposed.
• Self-surrender. If the judge lets the person report to prison on a later date, the sentence starts when the person arrives at the designated facility.
• Never before sentencing. A federal sentence cannot start earlier than the date the judge imposes it. Time in custody before that date is handled as credit, explained next.

Cases that involve a state sentence too, or a person brought to federal court from state custody, are more complicated. Who had the person in custody first, and what the federal judgment says about concurrent or consecutive time, can change the start date by months or years.

Do you get credit for time served in federal prison?

Yes, for time in custody before the sentence starts, if the law's conditions are met. Federal law says a person "shall be given credit toward the service of a term of imprisonment for any time he has spent in official detention prior to the date the sentence commences" (18 U.S.C. § 3585(b)) if that detention was:

1. because of the offense for which the sentence was imposed, or
2. because of any other charge for which the person was arrested after committing the offense of conviction,

and the time "has not been credited against another sentence."

That last condition is the one that causes the most trouble. Time that already counted toward another sentence, including a state sentence, does not count twice. "Official detention" generally means being locked up, such as in a jail or detention center. Time spent released on bail, even under strict conditions, is not. The Supreme Court held that a person who spent time in a treatment center while "released" on bail was not in "official detention" under § 3585(b) (Reno v. Koray, 515 U.S. 50 (1995)).

The BOP computes jail credit, not the judge

The Supreme Court has held that "it is the Attorney General who computes the amount of the § 3585(b) credit after the defendant has begun to serve his sentence," and that a district court cannot compute it at sentencing (United States v. Wilson, 503 U.S. 329 (1992)). The Attorney General acts through the BOP.

So a judgment that says "credit for time served" does not settle the question. The BOP still applies § 3585(b) on its own. The judge does have one related tool. In some cases where the person is also serving another sentence for related conduct, the judge can lower the federal sentence to account for time the BOP will not credit (USSG §5G1.3(b), 2025 Guidelines Manual). The Commission recommends that judges describe any other adjustment for an undischarged term as a sentence chosen under 18 U.S.C. § 3553(a), "rather than as a credit for time served," to avoid confusion with the BOP's authority under § 3585(b) (§5G1.3, comment. (n.4(E))).

How does good conduct time work?

Good conduct time (GCT) is credit the BOP awards for following prison rules. A person serving more than one year, other than a life sentence, may receive "up to 54 days for each year of the prisoner's sentence imposed by the court," if the BOP finds the person "displayed exemplary compliance with institutional disciplinary regulations" during that year (18 U.S.C. § 3624(b)(1)).

Key points:

• No good conduct time on sentences of one year or less. The statute applies only to a term of "more than 1 year."
• It is figured on the sentence imposed. The First Step Act of 2018 changed the wording to "each year of the prisoner's sentence imposed by the court." The BOP's regulation now says it awards up to 54 days "for each year of the sentence imposed," with a prorated amount for a partial final year (28 C.F.R. § 523.20(b)). The BOP's Sentence Computation Manual was written before that change and describes the older method, so the statute and the current regulation control where they differ.
• It can be lost. Disciplinary sanctions can reduce good conduct time (28 C.F.R. § 523.20(a)), and credit that was not earned "may not later be granted" (18 U.S.C. § 3624(b)(1)).
• Education matters. For offenses committed on or after April 26, 1996, the regulation allows up to 54 days a year for a person who has earned, or is making satisfactory progress toward, a high school diploma or equivalent (or a BOP-approved alternative), and up to 42 days a year otherwise (28 C.F.R. § 523.20(d)).

When a person arrives, the BOP "will initially determine a projected release date by calculating the maximum GCT credit possible," and that date "is subject to change during the inmate's incarceration" (28 C.F.R. § 523.20(b)(1)). So the first projected release date assumes perfect conduct.

How is a federal release date calculated?

The basic order is the same in most cases:

1. Find the start date under § 3585(a).
2. Add the full sentence to the start date. The BOP calls the result the full-term date.
3. Subtract jail credit under § 3585(b).
4. Subtract good conduct time under § 3624(b). The result is the projected release date.
5. Adjust for the calendar. If the release date falls on a Saturday, a Sunday or a legal holiday at the place of confinement, the BOP may release the person on the last weekday before it (18 U.S.C. § 3624(a)).

First Step Act time credits, explained below, do not change the release date itself in this list. They change where the last part of the sentence is served, or when supervised release begins.

A worked example

This example is simplified to show the order of the steps. It is not a prediction for any real case.

Say a judge imposes a 60-month (5-year) sentence. The person was arrested on the federal charge and spent 100 days in jail before sentencing. That time was not credited to any other sentence. The person stays in federal custody after sentencing, so the sentence starts on the day it is imposed.

Step	What happens	Effect
Sentence imposed	60 months	5 years from the start date
Jail credit, § 3585(b)	100 days before sentencing	100 days earlier
Good conduct time, § 3624(b)	Up to 54 days × 5 years	Up to 270 days earlier
Projected release date	Assumes all good conduct time is earned	About 5 years minus 370 days after the start date

In this example, the person would serve roughly four years in custody after sentencing, plus the 100 days already served before it. If some good conduct time is lost for discipline, the date moves later. If the person is eligible for First Step Act time credits, some of that remaining time may be spent in a halfway house or on home confinement instead of in prison, or supervised release may begin earlier.

How do First Step Act time credits and prerelease custody fit in?

The First Step Act lets eligible people earn time credits for taking part in approved programs and productive activities. The law says these credits "shall be applied toward time in prerelease custody or supervised release" (18 U.S.C. § 3632(d)(4)(C)):

• The BOP can use up to 12 months of credits to start supervised release early (18 U.S.C. § 3624(g)(3)).
• Other credits move the person into prerelease custody, meaning a halfway house or home confinement, sooner. The usual time limits on prerelease custody do not apply to time earned this way (18 U.S.C. § 3624(g)(10)).
• People convicted of offenses on the statute's list cannot earn these credits (18 U.S.C. § 3632(d)(4)(D)).

Separately from credits, the BOP can place most people in prerelease custody for up to the last 12 months of the sentence, with home confinement limited to the shorter of 10% of the term or 6 months (18 U.S.C. § 3624(c)).

For the details, see our guides to federal halfway houses and federal home confinement, our First Step Act summary, and our post on early release under the First Step Act.

How do I find a federal inmate's release date?

The BOP's public inmate locator shows a release date for most people in BOP custody. You can search two ways:

• By number. The BOP register number (format #####-###) is the most reliable. The locator also accepts a DCDC, FBI or INS number.
• By name. Enter a first and last name. A middle initial, race, age and sex help narrow the results.

The results show the name, register number, age, race, sex, release date and location. According to the BOP's notes on the locator, a release date in the future "reflects the inmate's projected release date based on BOP calculations." A release date of "UNKNOWN" means the term is not determined yet, for example because the person has not been sentenced.

Two cautions:

• The locator page itself warns that, because of the First Step Act, "sentences are being reviewed and recalculated" and "an inmate's release date may not be up-to-date."
• The locator date is not the whole picture. It may not show when the person is expected to move to a halfway house or home confinement.

The person in custody can ask the unit team, in writing, for a copy of the sentence computation and the latest First Step Act time credit assessment, and compare them with the judgment.

What if the BOP gets the jail credit wrong?

Mistakes happen, especially in cases with state custody, writs, or more than one sentence. Act early, because the remedy steps take time and a release date does not wait.

1. Use the BOP's administrative remedy process. This is the BOP's formal complaint system (28 C.F.R. § 542.10 and following; Program Statement 1330.18, Administrative Remedy Program):

• First try to resolve it informally with staff.
• Then file a formal request with the warden on form BP-9, within 20 calendar days after the event you are challenging (28 C.F.R. § 542.14(a)).
• Appeal to the Regional Director on form BP-10 within 20 calendar days of the warden's response, then to the General Counsel on form BP-11 within 30 calendar days of the regional response (28 C.F.R. § 542.15(a)). Extensions are possible for a valid reason.

Attach the judgment, records of any arrest and detention dates, and any state paperwork showing what time the state did or did not credit.

2. If that fails, go to federal court under 28 U.S.C. § 2241. A challenge to how the BOP is carrying out the sentence, including how it computed credit, is usually brought in a habeas corpus petition under 28 U.S.C. § 2241. It is filed in the federal district where the person is confined, usually naming the warden. The Supreme Court in Wilson noted that prisoners have been able to seek judicial review of these computations "after exhausting their administrative remedies," and courts generally expect the BOP process to be finished first. For more on § 2241 petitions and where to file one, see 2255motion.com's guide to § 2241 and the savings clause.

Common questions

Do you get credit for time served in federal prison?

Yes, if the conditions in the statute are met. A person gets credit for time in official detention before the sentence starts if it resulted from the offense of conviction, or from another charge for which the person was arrested after that offense, and the time was not credited against another sentence (18 U.S.C. § 3585(b)). The BOP, not the judge, computes that credit (United States v. Wilson, 503 U.S. 329 (1992)).

How is a federal release date calculated?

The BOP starts from the date the sentence began, adds the full sentence, subtracts jail credit, and then subtracts good conduct time of up to 54 days for each year of the sentence imposed (18 U.S.C. §§ 3585, 3624(b)). The first projected date assumes all good conduct time will be earned and can change later (28 C.F.R. § 523.20(b)(1)). First Step Act time credits can then move the person to prerelease custody or supervised release sooner (18 U.S.C. § 3632(d)(4)(C)).

How do I find a federal inmate's release date?

Search the BOP's inmate locator by register number or by name. A release date in the future is the projected release date based on BOP calculations (BOP, About the inmate locator). The BOP warns that dates may not be up to date while First Step Act credits are recalculated, so the person in custody should also ask the unit team for the current computation.

What if the BOP gets the jail credit wrong?

Start with the BOP's administrative remedy process: informal resolution, then a BP-9 to the warden within 20 calendar days, then appeals to the Regional Director and the General Counsel (28 C.F.R. §§ 542.14–542.15). If the error is not fixed, the usual court remedy is a habeas corpus petition under 28 U.S.C. § 2241 filed in the district where the person is confined.

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