How long is a human generation?

Answer 1

In the past, a human generation has been considered to be 20-25 years. Older genealogical documents will use these numbers.

According to dictionary.com, the definition of "generation" is a "term of years, roughly 30 among human beings, accepted as the average period between the birth of parents and the birth of their offspring."

However, genealogical studies have revealed that this is too simplistic and can result in large inaccuracies during statistical calculation.

According to Ancestry.com, a calculation based upon "three generations per century (33 years each) for male lines and 3.5 generations per century (29 years each) for female lines" leads to much more accurate estimates.