The Bible never tells us exactly how long Jesus lived on earth. Most of what we think about His age is based on educated guesses.
The age that a priest could enter public ministry was 30 years old. Correspondingly, Jesus began His public ministry when He was “about 30 years old” (Luke 3:23). This is really the only time reference that we have concerning Jesus’ age. When estimating how long Jesus lived, one problem is that the gospels never give (and do not claim to give) a comprehensive account of all of Jesus’ activities. However, most scholars believe, after a careful study of the gospels, that there is evidence that Jesus observed at least three distinct Passovers during His public ministry. Perhaps He celebrated more Passovers that we don’t know about, but, if there are at least three, then His public ministry would have lasted between 2 and 3 years. If you take “about 30” when He started public ministry and add “about three” more years of ministry, you get an age of about 33, which is the most commonly accepted age for Jesus when He died and rose again. Jesus might have been a bit younger—maybe 32—but He could also have been a couple years older if He observed Passovers that are not mentioned in the gospels.
Based on other dates and events, we know that Jesus could not have had a public ministry for much longer than a few years. According to the historian Josephus, the high priest Caiaphas, who presided over the plot to crucify Jesus, was in office until AD 36, and Pilate governed in Judea from AD 26 to 36/37, so the crucifixion must have happened before AD 36. If Jesus was born between 4 and 2 BC, which is commonly accepted as well, based on the date of Herod the Great’s death, then the maximum time span of Jesus’ life would have been 4 BC—AD 36. That would put Jesus’ age at the time of His crucifixion at 40, at the very oldest. So the answer for how long Jesus lived is anywhere between 32 and 40 years, but the best guess, and the most commonly accepted, is 33 years.
When discussing Jesus’ age, it is always important to point out that the 33 years of His life is only the time our Lord spent on earth. The Son of God had no beginning; His birth through the virgin Mary was simply His entrance into the human race. He is the eternal God and was already in existence “in the beginning” (John 1:1). Likewise, He is alive today, at the right hand of the Father (Hebrews 7:25) and will continue to live forever (Revelation 1:18).