Here is what the Smiths Bible Dictionary says for this :
Generation. In the long-lived patriarchal age a generation seems to have been computed at 100 years, Gen. 15:16, comp. 13, and Ex. 12:40; but subsequently the reckoning was the same which has been adopted by modern civilized nations, viz., from thirty to forty years. Job 42:16. Generation is also used to signify the men of an age or time, as contemporaries, Gen. 6:9; Isa. 53:8; posterity, especially in legal formulæ, Lev. 3:17, etc.; fathers, or ancestors. Ps. 49:19.
Below is some other general information about it online :
I think, the general rule of thumb from what I read online, is a new generation is created every 25 years ( but that varies from family to family ) . So, would you times the length of a generation , times 14 I guess ? . But It depends on how long that specific generation was also .
The word generation, can mean other things in language, aside from something biological.
Here is some information you can read :
Generation - Wikipedia, the free encyclopedia
Generation - Wikipedia, the free encyclopedia
search :
FYI: How Long is a Generation?