A life sentence ranges from 10 years to natural life depending on the state. See parole eligibility, LWOP rules, juvenile sentencing, clemency, and second look laws for all 50 states.
recordinglaw.com
State law dictates the length of the sentence that the prisoner has to serve before becoming eligible for parole. Total time served can be a percentage such as 85% of the period or a set number of years with the shortest life sentence being 2 years and the longest life sentence being the rest of the persons natural life. Sentencing for a life sentence can vary in length between
2, 10, 15, 20, 25, 40, or even 99 years. Once the life sentence or appropriate portion of the life sentence has been carried out and the inmate is eligible for parole, a parole board will decide whether the offender should be released on parole or sent back to prison.
A life sentence means you can spread your natural life in prison but not necessarily. The number specifies the minimum time. You can get out unless it's without the possibility of parole.