A human generation is generally seen to be 30 years. The adolescent stage for a person would be teen years. 20s and 30s are usually the years that people start having kids. 40s and 50s would be middle age for a human, where having kids is possible but unlikely. 60s and up are considered old age, where people are expected to retire and begin dying off.

I want my elf generations in this world to be equivalent to a human, but am unsure of the math. They live for about 250 years, and siblings are born decades apart. I don't want too many generations alive at the same time. The max should be a great grandparent. How can I make this possible?

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    $\begingroup$ Re "A human generation is generally seen to be 30 years", seen by whom? Perhaps in contemporary western society 30 years is a good approximation, though 25 seems better: time.com/4181151/first-time-moms-average-age In earlier times or other societies, it could be as little as 15 years. But for a society of long-lived individuals, the concept of generation is really meaningless. Even with humans, my late neighbor (died at 102) had grandchildren older than his youngest children. $\endgroup$
    – jamesqf
    Jul 16, 2018 at 6:06
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    $\begingroup$ I've always heard/seen "generation" used to define a 25 year block demographic, never 30 years. $\endgroup$
    – Ash
    Jul 16, 2018 at 10:27
  • $\begingroup$ @Ash In Western countries people are marrying and rearing children later. This is shifting the generation timing. Previously I'd have agreed with you that generation cohorts would be 25 years. The times they are a-changing. $\endgroup$
    – a4android
    Jul 22, 2018 at 5:26

7 Answers 7


All of the answers so far take a human life span and extrapolate to an elven life span. In that case I don't feel you have elves - but long-lived humans. There may be other elves with other rules, but using Tolkein's as the archetype we have a generation lasting about 100 years.

Their lives are made of 3 "cycles" - the first, being childhood and adolescence, lasting 100 years. And they have stopped growing by about 50

This 100 year number is also referenced in D&D 5th Edition.

However, toklein's elves were "functionally immortal", so it does not work to compress their life cycles down to 250 years. It also means we would struggle to prevent too many generations being alive at once.

"Elderly" is not a term normally associated with elves - so I would use whatever is causing this life expectancy as a plot point. Tolkein's elves "die of grief and weariness" - perhaps 250 years represents the maximum amount of grief and weariness which can be experienced in once lifetime? Or conscription/army service meant that in practice, very few/no elf survived past this point.

So, given your desired life expectancy of 250 - I'd say

0-50 Childhood

50-100 Adolescence

100-250 Child-rearing age (with a long tail - I suspect they'd be responsible enough to mostly not have children when they are 200+).


The math is easy. A generation is the average time between when a child is born and when it has children of its own.

  • 1 generation - parent and child
  • 2 generations - grandparent, parent, and child
  • 3 generations - great grandparent, grandparent, parent, child

Thus, if you want to only see great grandparents, you need to make things such that there are only 3 generations. If a lifespan is 250 years, then that means you want roughly 80 or 90 years between generations to accomplish your goal. (250 / 3 = 83.333...)

You can accomplish this in a few ways:

  • Biological - Your elves simply don't become fertile until they're nearly 100 years old. Historically we were driven heavily by biology, having babies very close to the first moment a woman can have babies.
  • Social pressure - Your elves might have a shorter biological youth, long social youth phase where they are not considered responsible enough to have a child, even though their bodies are ready for it. Generally speaking, most Westernized cultures are in this state. Women defer having children until they get married for the most part, and that happens quite a long time after they are physically capable of having children.
  • Personal pressure - Your elves may seek to accomplish something before having children. We are starting to enter this phase more and more ourselves. We are seeing women choosing to have children later in order to support having a career. As a parent myself, I love my child to death, but I appreciate the idea of a society where one leaves their mark before raising one. It's hard to leave a good solid mark on society when you have to pause half way through marking it to quick change a diaper, or to grab the green sippy cup (because the blue sippy cup they have in their hands is no longer good enough for them!)

Now, if you'll excuse me, I have to go.. Her-highness/my-daughter is demanding a horsie ride!


3.125 is your favorite number

This appears to be getting over-engineered and way too many people are distracted by your average number of years per generation. Let's focus on the question.

If the average human lifespan is 80 years (I'm rounding with the assumption that precision isn't as important as accuracy), then 250/80 = 3.125.

Can you not multiply everything by 3.125 and get what you want?

Making it all easy for the sake of Glarnak:

  • Puberty @ 40
  • Menopause @ 160
  • Retirement @ 200
  • # of fertile years: 120
  • Fertility rate: astoundingly low
  • Average generation in years...

OK, let's talk about "generations"

The problem with trying to identify the average time between "generations" is that (a) it's heavily based on when people marry, not biology; (b) the last child in line is the same generation as the first, despite a potential difference in age of 40 years (unlikely, but statistically possible); and (c) exactly when children are actually born (statistically early, not late, in a relationship).

So, for humans, if your average marrying age is 20 and your fertility range is menopause-marriage(not puberty) (31) and the average is between the oldest and youngest children (31/2 + 20)... your generation is (rounding) 35 years.

We all know that's a long honking time to reference generations. People tend to not have children that late in life... Our doctor thinks 40 is just a hair old for children due to the potential for defects, but let's use it. ((40-20)/2 + 20) = 30. And that's where Incognito gets his number.

Of couse, we all know that's high, too. I've seen 20 and 25 thrown around by medics and geneologists simply because most of the little bundles of joy are brought into the world in the first 10 years. Thus (10/2+20) = 25, which is what Jamesqf and Ash wanted to hear.

I like that one... let's use it. RND(25 * 3.125) = 78

  • Average generation in years: 80

If you want to make it a round 100 for your story, I don't think any of us will object.

And bob's your uncle.


Given the average human lifespan of ~75 years (in modern societies where 30 years/gen actually is in effect), with a 250 year lifespan, just take about 40% of it to get a nice round 100 year generation time.


Elves would reach their teenage years in their 40s - 50s, then their adolescent stage in their 60s - 100s. 130s to 160's would be their middle age, and 200 years and above would be considered old age. Each elven generation would be about 100 years.

Edit: I got these values by simply dividing each human year you provided with the average human lifespan of 75 years. That gave me a number which I multiplied with 250 years to get the appropriate year(s) in an elf's life for that stage. I did this to keep the same number of generations you wanted.

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    $\begingroup$ If you could add some rationale to those numbers, this could be a good answer. $\endgroup$
    – L.Dutch
    Jul 16, 2018 at 5:28
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    $\begingroup$ The logic is not necessarily correct. Elves could have a childhood/adolescense not much longer than humans, then an adulthood of several centuries, followed by (if they aren't killed beforehand) a short old-age period. $\endgroup$
    – jamesqf
    Jul 16, 2018 at 6:09

What is wrong with some elf families having multiple generations alive at the same time? I am descended from a woman who lived to see the birth of a few of her many great great grandchildren, I believe that the Guinness record for most living generations is 5 or 6, and there is a story about a Chinese family in the Tang Dynasty that had 9 generations living in the household.

At the Royal Ark site - India - Pensioners - Delhi - Page 20 The Family of Mughal Padishah Bahadur Shah II (1775-1862) is listed.


Bahadur Shah II's oldest of many sons was H.R.H. Shahzada Muhammad Dara Bakht, Miran Shah, Wali Ahd Bahadur [Mirza Shubu Sahib] 1790-1849, born when his father was 15. His oldest son was Mirza Muhammad Adu Afghan Bakht Bahadur [Mirza Kale Sahib]. b. 1804, educ. privately. m. Mubarak un-nisa (b. 1819; d. after 1862). He d.s.p. after 1863, born when his father was 14 and his grandfather 29.

The oldest grandson to have children was Mirza Muhammad Karim us-Shuja Bahadur. He was born in 1826 when his father was 36 and his grandfather 51 and died after 1849.

Mirza Muhammad Karim us-Shuja Bahadur's sons included Mirza Azim us-Shan Bahadur, born 1846, when his father was 20, his grandfather 56, and his great grandfather was 71, and Mirza Ahmad Shah Bahadur, born 1848 and had a daughter.

Meanwhile Bahadur Shah II had a bunch of other sons, including a 21st son Shahzada Mirza Muhammad Sher Shah Bahadur who was born in 1846, the same year as his oldest grand nephew, and was alive in 1856, and a 22nd son named Mirza Muhammad Sulaiman Shah Gorgani.

So that is an example of a man whose youngest son was born in the same year - or possibly a later one - as his oldest great grandson, and an example of generations in the same family overlapping in age.

Here is an interesting thread:


Here is a list of oldest fathers, although it focuses more on recent cases than historical ones:


I note that an ancestor of mine was born when his father was 50, and that father was 60 when his youngest daughter was born.

Here is a list of women who became pregnant after age 50:


Here is a list of youngest birth mothers:

https://en.wikipedia.org/wiki/List_of_youngest_birth_mothers 5

Here is a list of youngest birth fathers. They are all recent cases and don't include many historical cases.


Here is a list of some royal extremes in British royalty:

At 15, Henry IV is the youngest King to father a child, prior to his accession. The youngest queen regnant to give birth is Mary II, who gave birth to a stillborn child in 1678, prior to her accession, when she was just 16. The youngest mother to give birth to a monarch was Lady Margaret Beaufort, wife of Edmund Tudor, who was months from turning 14 when she gave birth to Henry VII in 1457.

The oldest parent was Edward I, who fathered his last child, Eleanor, in 1306, when he was 66, almost 67 years old.

The oldest mother was Eleanor of Aquitaine, who gave birth to John, in 1166, when she was 44.


Note that thousands or millions of people are descended from King John, and many thousands are descended from Henry VII, despite the extreme old and young ages of their mothers.

King Edward I, born in 17/18 June 1239, was 62 years, 1 month, and 18 days older than his second youngest child Edmund of Woodstock, 1st Earl of Kent (born 5 August 1301), who has many descendants among modern royalty and nobility.

There are many examples in history where the generations from oldest son to oldest grandson to oldest great grandson and so on have quite low average generation lengths and also many examples, usually from youngest son to youngest grandson to youngest great grandson, etc. have high average generation lengths.

If your elves live for about 250 years, you could make the average elf generation about 50 years, so that an average elf dies about when his/her fifth generation of descendants are born.

If you want three living generations with 250 year lifespans, you could make the average generation about 75 years and elf great grandchildren will be born about 25 years before the great grandparent dies.

Or you could make the average generation 100 years and average elves will died when their grandchildren are 50, and elves would only live to see great grandchildren when their generations are shorter than average or they live to be 300, 1.2 times the average lifespan.

It takes simple mathematics for you to combine elf lifespans and elf generations lengths to give the average elf family the number of living generations living at the same time that you desire. But some elf families will be different from the average and other elves may be favorably or unfavorably impressed with the differences.


I think you'd need to consider the biological reasons why humans are adolescent till about 20. This has to do with Brain development, and personality maturing. It also has quite a bit to do with local culture.

You could also consider the impact such a lifespan is likely to have on society.

Putting these 2 things together, I'd expect to see "youth" last until around the 50 year mark for your Elven species.

I'd expect to see "Elderly" last a similar timeframe as for humans. The main reason it is around the 15- 20 year mark for humans is that being Elderly has all sorts of mortality risks associated with it.

This means I'd see Elderly for your Elves to be around 220 - 230, with a natural progression into Senescence at 250.

So you'd be looking at an Adult period from around 50 to around 220.

Part of having kids is planning to be around until they reach (mostly) Adulthood themselves. I'd suggest your Elven society would see around 180 as the age to stop having children.


  • 0 - 50 Children Progressing to adulthood
  • 50 - 180 Adults that will continue having children periodically
  • 180 - 220 Adults that are in "retirement"
  • 220 - 250 Elderly

Does this give sufficient benchmarks to base a society around? I suspect cultural factors will have a huge part to play in something like this.

  • 1
    $\begingroup$ "Adolescence" is in part cultural. Go back a century or two, and you see many examples of people taking on adult responsibilities at 15 or so. $\endgroup$
    – jamesqf
    Jul 16, 2018 at 17:20
  • $\begingroup$ @jamesqf You're right. Have edited answer to add cultural to the reasons for adolescence $\endgroup$
    – kiltannen
    Jul 16, 2018 at 22:30

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