So first, it is stated that Midoria is the 9th user of OFA, the NINETH generation.  If we think about generations, that isn't a very reliable source of judging age. But we do know that AFO I'd 9 generations old.

From what I've seen on some fanfics, people say AFO is 100 years old, and since, as I said above, generations isn't the best form of measuring age, that would be believable. But that would also mean that each holder of OFA had, on average, 11.1 years of using OFA and training a successful, and that's including Midoria.

Now take ALL MIGHT. It is implied, or at least how I have interpreted what we know about his past, that ALL MIGHT was a teen, not any older than Midoria when he got OFA, mainly because he went to UA High. Some people have debated ALL MIGHT's age, but I feel the most believable is 50's-60's. So ALL MIGHT had OFA for 35 to 45 years before passing the torch.

And we can assume that AFO didn't kill his brother,at least until he absolutely had to.  Mainly because he cared for his brother enough to give him a quirk when it was thought he was quirkless. I'm gonna say that AFO gave his brother at 30 years of age. So AFO brother wat 30 when OFA was created. And let's say he also waited till he was 60, meaning already we have AFO being 95-105 years old.

We don't know, and probably won't find out how long the other 6 holders (Midoria is not included because as of now he hasn't had OFA for a year yet) so I'll average them out at 25 years of having OFA (including training the successor) each.  Which comes out at 150 years, so total is 245-295 years old, conservatively.

We could also assume that the average was 25 years, which would be 210 years, which totals at 305-315 years old.

Meaning AFO is a minimum of 245 years old, but probably closer to 320 years of age.

And that's if AFO and the first OF A user were brothers. Siblings can be 7 years apart, or even 10. With that in mind, AFO could be 330 years old if he's ten years older than his younger brother.

Comment your thoughts, ideas, or other theories about AFO's age.

* AUTOR'S NOTE*

I'm probably not gonna update this very often, pretty much if I think of a Theory or see a theory that interests me.
Keep that in mind and thanks for reading an idea I had about ten minutes ago and had to look into it more and let anyone who reads this know.
You can disagree, or add to the theory in the comments, or even just create a random story in the comments if you want, just don't make fun of people, or me, if you don't like their theories.

Banfan1 out.
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Cheeseburger.
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🍔
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I'm done now