Short answer. From six years and one day to twelve years. Article 27 of the Revised Penal Code fixes the duration of prision mayor — and of temporary disqualification imposed alongside it — within that range, unless disqualification is an accessory penalty, in which case its duration instead follows the principal penalty.
What the law says
The duration of the penalties of prision mayor and temporary disqualification shall be from six years and one day to twelve years
Revised Penal Code, Article 27 — Duration Of Penalties. Read the full provision →
What the law says
except when the penalty of disqualification is imposed as an accessory penalty, in which case its duration shall be that of the principal penalty
Revised Penal Code, Article 27 — Duration Of Penalties. Read the full provision →
Six years and one day to twelve years
Article 27 provides that the duration of the penalties of prision mayor and temporary disqualification shall be from six years and one day to twelve years. Prision mayor is grouped together with temporary disqualification in this range, meaning both penalties share the same span of six years and one day up to twelve years, with the exact sentence within that span depending on the specific offense and any modifying circumstances involved.
The disqualification exception
The article carves out an exception for temporary disqualification specifically: except when the penalty of disqualification is imposed as an accessory penalty, in which case its duration shall be that of the principal penalty. When disqualification rides along as an accessory to some other principal penalty, rather than standing as its own sentence within the six-to-twelve-year range, its length simply tracks whatever duration the principal penalty carries instead.
Where prision mayor sits among the other durations
Article 27 sets out a ladder of durations across several penalties: reclusion temporal runs from twelve years and one day to twenty years, immediately above prision mayor's range; prision correccional, suspension, and destierro run from six months and one day to six years, immediately below it. Prision mayor sits in the middle of this scale, above the correctional-level penalties and below reclusion temporal. Below those sit arresto mayor, from one month and one day to six months, and arresto menor, from one day to thirty days. At the top, the article deals with the perpetual penalties: a person sentenced to one of them shall be pardoned after undergoing the penalty for thirty years, unless by reason of conduct or some other serious cause the Chief Executive considers the person unworthy of pardon.
What this range does not resolve
Article 27 fixes the outer boundaries of prision mayor's duration but does not itself determine where within that six-to-twelve-year range a particular sentence falls — that depends on the specific offense charged, its prescribed penalty, and any aggravating or mitigating circumstances and other sentencing rules that apply to the case, none of which this article addresses directly. Nor does it say how much of the term must actually be spent in confinement before release becomes possible; it fixes the duration of the penalty, not the manner in which it is served.