How much percent of time do you serve in federal prison?

An inmate will serve 85% of the sentence imposed by a federal judge. 54/days per yera credit off the total sentence imposed, unless he loses it while in prision.

Good time begins accruing after the 1st year of incarceration. If your boyfriend has a high school diploma, he will be eligible for 52 days of good time credit per year following the 1st year (less if he does not have a high school diploma or its equivalent ).

85% is correct although the way it is calculated it works out to something like 87%.