August 5, 2026
Understanding Your Federal Sentence Term and Start Date
Educational companion to the Prison Professors sentence projection calculator
Planning note: This article provides general educational information. Only the Bureau of Prisons can make an official sentence computation, eligibility finding, credit decision, treatment decision, or placement decision. Policies and individual facts may change the result.
What “sentence length” means
Federal law directs the BOP to treat multiple concurrent or consecutive imprisonment terms as a single aggregate term for administrative purposes. Consecutive terms generally add together. Concurrent terms generally overlap, so a person should not simply add them. A mixed judgment—such as some concurrent counts and another consecutive count—may require a formal BOP computation.
The calculator does not decide how several judgments interact. It expects the user to enter the total aggregate federal term after that question has been resolved. If the BOP has already prepared a sentence computation, that document provides the better input.
When the federal sentence begins
Under 18 U.S.C. § 3585(a), a federal term ordinarily begins when the person enters custody to begin serving it or voluntarily surrenders at the designated facility. The calculator uses the date supplied by the user as that starting point.
Prior-custody credit presents a separate question. Section 3585(b) allows qualifying credit for official detention that has not already been credited against another sentence. The simplified calculator does not collect those facts and should not be used to resolve them.
Why calendar dates matter
A sentence imposed in months runs through actual calendar months. Month endings and leap years can shift a projected endpoint. The calculator uses calendar-date arithmetic instead of assuming that every month contains the same number of days.
For the common sentence of twelve months and one day, the calculator uses 12.01 as a special entry convention. It means twelve calendar months plus one day—not 12.01 decimal months.
Build and verify the record
Keep the judgment, statement of reasons when available, surrender order, designation notice, and any documentation of prior detention.
After the BOP completes the sentence computation, request a copy or review it with Correctional Systems staff. Confirm the aggregate term, commencement date, prior-custody credit, and projected release date.
If something appears wrong, ask a precise question supported by the relevant judgment or custody record. A clear paper trail helps staff evaluate the issue; it does not predetermine the answer.
Primary sources and further research
18 U.S.C. § 3584 — concurrent, consecutive, and aggregate terms
18 U.S.C. § 3585 — commencement and prior-custody credit
BOP Sentence Computation Manual, Program Statement 5880.28
A practical reminder
Use projections to prepare, not to make promises. A person can strengthen the record by acting consistently, documenting progress, addressing assessed needs, preparing for release, and communicating respectfully with staff. A strong record may support informed discretionary decisions, but it never guarantees a particular result.
If you are entering the prison system—or supporting a loved one who is—we encourage you to use the free tools at Prison Professors. Start by building a profile that memorializes the journey: goals, decisions, completed work, lessons learned, service, relationships, and release preparation. Develop the profile over time so it shows sustained growth rather than a last-minute collection of documents.
For this topic, preserve the judgment, sentence computation, custody-credit records, surrender documents, and written questions or responses about the official calculation.
A well-developed profile may support self-advocacy during imprisonment, on supervised release, or when seeking relief such as early termination of supervised release or executive clemency. It cannot guarantee a discretionary outcome, but it can give decision-makers a clearer factual record. To learn how to build and develop one, use our free workbook: Playbook: Become the CEO of Your Life.