Our answer to this question is always, "well, it matters," which is quite unsatisfactory for our clients. If one is sentenced to jail, there are various factors that determine how long one will stay in jail as a percentage of one's actual sentence. The biggest factor is the inmate count, or how filled up is the jail. The higher the inmate count, the more likely the jail will release one early. Other factors include one's medical condition, if one has prior convictions, if the crime was violent, if the crime involved the use of a weapon and one's gender.
If one is sentenced to prison, the discussion is somewhat easier once the sentence is determined. If the conviction is for a non-violent felony offense and the client has no prior felony convictions, the client will be eligible for release once he or she has served fifty percent of the total sentence, provided good behavior is maintained (Penal Code 2933(b)). If the client has served prior prison time, the client will have to serve at least eighty percent of the total sentence (Penal Code 667(b)(5)). If the crime is a serious or violent felony, the individual must serve eighty-five percent of the sentence (Penal Code 2933.1). Lastly, with certain crimes such as murder and kidnapping, there is no prison term reduction. The client must serve the entire sentence (Penal Code 2933.5).

When a client is sentenced to consecutive terms, the client must serve the longest sentence in its entirety, plus one-third of the mid-term for each remaining sentence (Penal Code 1170.1(a)). For example, if one is sentenced to three consecutive sentences for the same offense and the crime has a minimum term of three years, a mid-term of six years and a maximum term of ten years, the individual would serve the full ten year sentence (the longest sentence), plus four more years, or one-third of six years, twice. The total sentence would be fourteen years.
The tricky part of any determination of how much time one will actually serve is predicting the sentence. The Penal Code may set forth a minimum, mid-term and maximum sentence. The sentence will consequently be one of the three amounts, depending upon factors in aggravation and mitigation. Factors in aggravation may be, in a theft, the position of trust a victim had with the defendant, the defendant's refusal to cooperate with police and the amount stolen. Factors in mitigation may be the defendant's youth, his lack of a prior record and the entry into a plea bargain early in the case.
Sentencing enhancements come next. These factors add time to the total sentence. Some of the more common enhancements include a prior conviction for a strike offense, which can double the sentence. Also, if a firearm was used in the commission of the crime, the sentence may be increased by ten years (Penal Code 186.22 and 460(a)). Also, if the crime was committed as a gang member for the benefit of the gang, ten years can be added to the sentence (Penal Code 12202.54).