The Buddha's Lifespan

In certain kalpas, the lifespan of a Buddha and the lifespans of sentient beings are both very long, measured in kalpas. One small kalpa is 16.8 million years; a Buddha's lifespan can manifest for twelve small kalpas, or even longer, depending on the wholesome karma accumulated by the Buddha when He was a bodhisattva, and also on the karmic force of sentient beings. But this is only a manifestation; the actual lifespan of a Buddha is immeasurable—He can live indefinitely, without any limitation of time. Śākyamuni Buddha's lifespan in this Saha world was eighty years, similar to the hundred-year lifespan of sentient beings at that time, which was determined by the karmic force of sentient beings. Śākyamuni Buddha could have remained in the Saha world for more than a kalpa, but sentient beings lacked the merit to attract such a superior retribution, and the Buddha's prolonged presence would have brought no benefit to Buddhism or to sentient beings. Therefore, the Buddha manifested an eighty-year lifespan in accordance with conditions.