The federal-prison.org sentence calculator shows the total time that an inmate can expect.
When a person is sentenced to federal prison, the BOP automatically assumes that 100% of the Good Conduct Time for which each inmate is eligible will be awarded. They calculate the release date with this in mind. Due to some questionable logic in the interpretation of the law on part of the BOP, calculating the time to be served on a federal prison sentence can be rather confusing. Contrary to popular belief, one cannot arrive at the total time to be served by simply deducting 15% from the sentence duration.
The federal-prison.org sentence calculator shows the total time that an inmate can expect to serve in federal prison assuming that they behave and are awarded all Good Conduct Time for which they are eligible. Some of this time may be spent in a halfway house. All inmates are to be considered for up to 12 months of halfway house time. Technically, an inmate may be placed at a halfway house for longer than 12 months, but this is rare. Some inmates may be eligible for a further reduction on their sentence of up to 12 months for participation in the Residential Drug Abuse Program (RDAP).
For more details on halfway houses, RDAP, and for a list of offenses that can result in lost Good Conduct Time, please see The Book.