How is Good Conduct Time calculated?
Federal prisoners serving more than one year earn up to 54 days of Good Conduct Time for each year of the sentence imposed, under 18 U.S.C. § 3624(b). Since the First Step Act of 2018, the 54 days are computed on the sentence the judge imposed, not on time actually served — which is why a person with clear conduct serves roughly 85% of the sentence. GCT is credited as earned each year and can be reduced for disciplinary violations, but it is separate from — and stacks with — First Step Act earned time credits.
Reviewed against 18 U.S.C. § 3624(b) and BOP Program Statement 5880.28 (Sentence Computation Manual). Last updated .
How many days of good time per year — and per sentence?
The rule is one line of statute: up to 54 days for each year of the prisoner's sentence imposed by the court, prorated for any partial final year. Because the credit comes off the end of the sentence, the practical effect is that each sentence-year takes about 311 days to serve with full credit.
| Sentence imposed | Maximum GCT | Time served with full GCT |
|---|---|---|
| 12 months and 1 day | 54 days | ~10.2 months |
| 24 months | 108 days | ~20.4 months |
| 60 months | 270 days | ~51 months |
| 120 months | 540 days | ~102 months |
| 240 months | 1,080 days | ~204 months |
Worked example
60-month sentence, custody 2026-01-15, clear conduct
- Full-term date: 2031-01-14 (60 months from custody, minus 1 day).
- GCT: 5 years × 54 = 270 days.
- Projected GCT release: 2031-01-14 − 270 days ≈ 2030-04-19.
- That's before any First Step Act credits, RDAP, or halfway-house time.
What did the First Step Act change about the 54 days?
Before 2018, BOP read § 3624(b) to award 54 days per year of time served, which worked out to about 47 days per sentence-year — the Supreme Court upheld that reading in *Barber v. Thomas*, 560 U.S. 474 (2010). Section 102(b) of the First Step Act rewrote the statute to say what most people always assumed: 54 days per year of the sentence imposed. The change was retroactive in effect, and its implementation in July 2019 moved thousands of release dates earlier by roughly a week per sentence-year.
If a sentence computation predates mid-2019 and was never rerun, or if the math on a current computation works out closer to 47 than 54 days per year, that is worth a written question to the case manager and, if unresolved, an administrative remedy.
How is the final partial year prorated?
For a sentence that isn't a whole number of years, the last partial year earns GCT pro rata — 54 days scaled by the fraction of the year. A 66-month sentence is 5 years (270 days) plus 6 months (~27 more days), about 297 days total. BOP's day-level rounding conventions live in Program Statement 5880.28, and at least two circuits have litigated the proration method — the OutDate calculator applies the circuit-aware rule when you provide the sentencing district.
Can Good Conduct Time be taken away?
Yes — GCT is credited "subject to determination by the Bureau of Prisons that, during that year, the prisoner has displayed exemplary compliance with institutional disciplinary regulations." Disciplinary hearing officers can disallow GCT for the year in which a violation occurred (the amounts are set by the disciplinary severity tables in 28 C.F.R. part 541), and disallowed time is generally not restored. This is different from First Step Act credits, which have their own loss-and-restoration rules.
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The free OutDate calculator applies these rules to a real sentence — Good Conduct Time, First Step Act credits, halfway house and RDAP dates — with every assumption listed next to the answer. No account needed; nothing is stored.
Open the federal release date calculatorFrequently asked questions
Is it 54 or 47 days of good time per year?
54 days per year of the sentence imposed, since the First Step Act of 2018 amended 18 U.S.C. § 3624(b). The old 47-days-effective calculation (54 per year served) is obsolete — a current computation should never use it.
What percentage of a federal sentence do you serve?
With full Good Conduct Time, about 85.2% (54/365 ≈ 14.8% credit). First Step Act credits, RDAP early release, and halfway-house placement can each reduce time in prison further — many eligible people serve well under 85% in custody.
Does time in county jail before sentencing count?
Prior custody credit under 18 U.S.C. § 3585(b) counts qualifying pre-sentence detention toward the sentence, and GCT is then computed on the full sentence. Jail credit is a separate line item on the computation — check it, since missing jail credit is a classic computation error.
Do sentences of a year or less earn good time?
No. Section 3624(b) applies to terms of imprisonment of more than one year. A sentence of exactly 12 months earns nothing; 12 months and one day earns 54 days.
Primary sources
Everything on this page is drawn from the statutes, regulations, and BOP program statements below — read them directly:
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Estimates, not promises
This page describes federal law and Bureau of Prisons policy in general terms for education. It is not legal advice, it doesn't account for the facts of any individual case, and no attorney–client relationship is created by reading it. The BOP makes all final release-date determinations. Have an attorney review anything before you file it. Built by OutDate, the federal release date calculator.