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How the calculator works

The rules it follows, in plain language, with the law or BOP policy behind each one.

Rules change, and BOP's own sentence computation controls. Use the estimate to plan and to ask good questions.

This is information, not legal advice. Ask your attorney.

This calculator estimates dates using the rules the Federal Bureau of Prisons (BOP) follows. It is an estimate, not BOP's computation, and not legal advice. One incident report, a late risk assessment, a change in BOP policy, or a lack of halfway house space can move any date. Questions about the sentence itself go to the attorney.

The steps, in order

  1. Full term. The sentence runs from the day it started, counting that day, for the months the judge imposed. If it started on a day the last month doesn't have (like the 31st, or the 29th going into February), it ends on that month's last day. Days spent in federal custody before the sentence started ("jail credit") come off the end. (18 U.S.C. § 3585; BOP Program Statements 5880.28 and 5880.30)
  2. Good conduct time. Up to 54 days for each year of the sentence imposed. A partial final year earns a share of 54 (0.148 of a day for each day, rounded down). Sentences of one year or less earn none, which is why 12 months and 1 day often ends sooner than 12 months. Without a GED, or progress toward one, the rate is 42 days a year. Incident reports can take good time away. (18 U.S.C. § 3624(b); 28 CFR § 523.20; 87 FR 7938, Feb. 11, 2022)
  3. RDAP. Finishing the Residential Drug Abuse Program can take up to 6, 9 or 12 months off, depending on the sentence in whole months (30 months or less, 31 to 36, 37 or more), if BOP finds the person eligible. It comes off before First Step Act credits. After the residential part, the program needs at least 120 days of treatment in a halfway house or on home confinement, so release can't come sooner than 120 days after the residential part ends. If needed, BOP uses fewer First Step Act credits toward supervised release to make room. (18 U.S.C. § 3621(e); 28 CFR § 550.55; BOP Program Statements 5331.02 and 5410.01)
  4. First Step Act time credits. 10 days for every 30 days of programming, and 15 days once the person has had two risk assessments in a row at Minimum or Low. Credits post only in full 30-day blocks. Up to 365 days of credits can start supervised release earlier, but only if the sentence includes supervised release. Credits beyond that move up the date for a halfway house or home confinement. Jail credit days never earn credits. From Sept. 30, 2026, credits can start when the sentence starts, even before arriving at the assigned prison. Some offenses can't earn credits at all. A detainer or a final order of removal doesn't stop someone from earning credits, but BOP can't use them while it is in place. (18 U.S.C. § 3632(d)(4); 28 CFR §§ 523.40–523.44; interim final rule effective Sept. 30, 2026)
  5. Risk level. Credits can be used only once the last two risk assessments in a row are Minimum or Low, or a warden approves a petition. Someone at Medium or High risk still earns credits but can't use them until then. (28 CFR § 523.44) If you don't enter their risk scores, the calculator counts the slower rate, 10 days for every 30, the whole way. If you pick a level or a date for the second Low score instead, it uses that. Either way it says what it assumed, right next to the release date.
  6. Halfway house and home confinement. The Second Chance Act allows up to 12 months in a halfway house, and home confinement for the last 10% of the sentence or 6 months, whichever is shorter. These are counted back from the date First Step Act credits set. BOP decides the amount after a five-factor review, and halfway house space can delay a move. (18 U.S.C. § 3624(c); 18 U.S.C. § 3621(b); 28 CFR § 570.22; BOP directive, June 17, 2025)
  7. Supervised release. Credits can start supervised release up to a year early; they don't make it shorter. After one year, a person can ask the court to end supervision early. (18 U.S.C. § 3583(e)(1))

What the calculator can't know

  • The levels and dates of past and future risk assessments, unless you enter them.
  • Incident reports and lost credits, unless you add them.
  • Whether a specific offense is excluded from First Step Act credits. The FSA Time Credit Assessment sheet says.
  • Halfway house space where they are going home.

Check it against BOP's own sheets

Ask the unit team for the FSA Time Credit Assessment and the Sentence Monitoring Computation Data. Compare the projected release date, the FSA conditional release date, the FSA conditional placement date, and the Second Chance Act placement date. If a number doesn't match, bring both to the next team meeting and ask which input is different.

Sources

  • 18 U.S.C. §§ 3583, 3585, 3621, 3624, 3632 — law.cornell.edu/uscode/text/18
  • 28 CFR § 523.20 (good conduct time); §§ 523.40–523.44 (First Step Act time credits); § 550.55 (RDAP early release); §§ 570.21–570.22 (halfway house time and review) — ecfr.gov
  • Good Conduct Time Credit Under the First Step Act, 87 FR 7938 (Feb. 11, 2022) — federalregister.gov
  • First Step Act Time Credits Revisions, interim final rule effective Sept. 30, 2026 — federalregister.gov
  • BOP Program Statements 5880.28 and 5880.30 (Sentence Computation Manuals), 5410.01 (First Step Act Time Credits) and 5331.02 (RDAP early release) — bop.gov/policy/progstat
  • BOP directive on First Step Act credits and the Second Chance Act (June 17, 2025) — bop.gov/news
  • GAO-26-107353, on transfers to halfway houses and home confinement (Feb. 11, 2026) — gao.gov

Rules reviewed October 25, 2026.

This is information, not legal advice. Ask your attorney.