The Bible does not give a direct answer to this common question. Yet it does leave us with some observations. When we study the Scriptures, it becomes clear that the length of a generation differs from one historic period to the next. The generations of the earlier history of man were longer, because people lived longer and tended to marry later in life.
One of the genealogies in the New Testament says this: “So all the generations from Abraham to David are fourteen generations, from David until the captivity in Babylon are fourteen generations, and from the captivity in Babylon until the Christ are fourteen generations” (Matt. 1:17, NKJV).
Each of these three groupings were summed up as 14 generations. Yet, they did not last the same number of years. In fact, the average generation in the period from Abraham to David was approximately 64 years. But, the average generation from David to the Babylonian captivity and from that captivity to Christ was about 38 years.
The term “generation” may have other meanings too. The “generation” that sees Christ’s return, for example, refers to all the people living at that time.