If you did not know Ranma's age how old would you say he is?

[A.Nonymous]

I noticed in the Prize eating scene, when Ranma explains who Shampoo is that Ranma-chan looks about 9... Also whenever she's trying to convince Ryoga that she's his sister or fiancée or something she looks a lot younger.
There was this weird anime that showed up for a while on Adult Swim. It was about a delinquent highschool...similar to Furinkan. One of the characters looked like a 35 year old cossak.
I'm guessing Ryoga is really 24 and got held back a few years in Jr. High... probably because he couldn't get someone to lead him to school in the morning.
Kuno though, when he ate the 17 inch mushroom he stole from chibi-ranma found it "refreshing" which tells me he's as big an idiot as Ryoga and lost a few years from the mushroom.

[Zwzn]

In terms of physical appearance, Ranma looks too old to be 14. No way any 14 year old has a body that looks that mature.

I have seen 5th graders(2) in my grade school that could pass as being at least a couple years older then they were. Secondly it seems to me that it depends on which pictures/frames you are looking at. This is most noticeable with Ranma's female form in my opinion. In the end it is all a matter of opinion.

[EdenB]

If I didn't know Ranma's age, i'd of said based on how he physically looks that Ranma is 16 and Ranma girl-type is 14.
If it was gauging based on personality, i'd proberly not answer. Growing up constantly trained by Genma would proberly make him incredibly mature in some ways (taking pain, etc) and incredibly immature in others (dealing with people). It'd be harder to guess.

[A.Nonymous]

Atlan, this is Japan you're referring to. A place in which - up until the fall of 1994, which was near the end of the manga publishing - the legal age of marriage (with parental consent) was 16 for boys and 13 for girls.

You know, that makes sense given the initial premise of the Ranma series. We're dealing with a Japanese version of "Tootsie." Where Ranma (A GUY) is being subjected to all the indignities usually reserved for the "girl" in an arranged marriage (and the society in general).
There is no reason to believe that Akane's age is being misrepresented (by Soun if anyone) as "16," the age at which a "MALE" could legally marry in Japan (with parental consent). While with Ranma, we are in effect taking Genma's word that Ranma is "16" and not actually "13..."
Hell, given Genma's track record I was always surprised he never forged Ranma's name to a marriage certificate and snuck it in...maybe he did and it got sent back with a "what were you thinking" notice.
The truth is, I think the only reason Ranma and Akane weren't forced to marry on the first day, other than it not fitting in Takahashi's plot, is that there's traditionally a year long period to get to know one another in an arranged marriage.

Sorry for being a bit harsh here, but you simply cannot view Japanese society with Western social values, even today, and far too many American & European anime fans try to do exactly that.

No, I think it's just an American thing... You can almost smell the Evangelical Christian values. And these were the people who not so long ago were marrying their sisters and cousins at 13. Wasn't there a Ranma/Tenchi cross where Ranma called Ayeka a hillbilly for tossing aside her own brother for his grandson...her great-nephew.

[Nekomata-sensei]

No, I think it's just an American thing... You can almost smell the Evangelical Christian values. And these were the people who not so long ago were marrying their sisters and cousins at 13. Wasn't there a Ranma/Tenchi cross where Ranma called Ayeka a hillbilly for tossing aside her own brother for his grandson...her great-nephew.

Link?
But yeah, I agree with the whole idea that Ranma is facing the indignities usually reserved for a girl, which makes it all the more believeable that Ranma is actually 13/14. Repeatedly in the series, Akane is masculinized, and Ranma is feminized.
In fact, if you ignore the whole Akane hitting Ranma thing, you could conveivably switch the whole harem genre thing from Ranma to Akane, who also possesses multiple suitors, and play Ranma as the sort of 'exotic girlfriend' who is strange and rude, but perfect at everything inculding looks and has supernatural abilities to deal with enemies and rivals. Ranma is shown to have many skills accociated with women, he's good at cleaning (and is a compulsive neat freak who cleans up Hinako-sensei's apartment for her), he can cook (to a certain level), makes an excellent waitress, looks beautiful in womens clothing (in girl form at least...), is a shameless flirt, pulls and endless number of costumes and different clothing out of nowhere (and a mallet on a few occasions...), and has all the skills expected of a traditional girl that Akane doesn't have, except for manners and feminine speach. While on the other hand, Akane is masculinized, insecure, unsure of who she really likes, (Do I like the exotic girlfiend, Ranma, the exotic rival of the exotic girlfriend, Ryoga, or the 'girl next door' (er... man...) Dr. Tofu?) is clumsy, good at sports, and attracts and endless stream of obsessive suitors...
Back to Ranma's age, I don't think, even in the mushroom arc Genma, or anyone else explicitly states Ranma's true age, or implies a birthday. The _assumption_ is that Ranma is about 16. But knowing how Genma raised Ranma, and from visual and verbal cues in the manga based on Ranma's behavior, Ranma is at least less mature than 16 mentally.
I think one of the key things that keeps it vauge, is that we never really get to see Ranma's grades, it's implied they are bad, or at least that Ranma struggles with schoolwork sometimes and tries to keep his grades secret. But it's very likely as well that Ranma is some sort of genius (due to his quick learning ability when it comes to the martial arts) and has skipped grades, knowingly or not, and Ranma's only in Akane's grade because Genma wants him to be.
But when it's all said and done, Ranma still ate the 16 inch mushroom, so by the end of the manga, at least phsycially, Ranma is 16, in both forms.

[antimatterenergy]

Actually we have no proof Ranma ate the 16 cm mushroom because we never see it it is just assumed that he ate the 16cm one.
I don't know are Ranma's grades really bad? In the manga we never see Ranma's grades and we aren't told about them. There are some things we do know though. We know Ranma misses/skips school fairly often, acts up and sleeps during class, doesn't care for school, and is a delequint because he doesn't act the way he's expected to. Judging by that it is easy to assume that Ranma doesn't do well in school but really we have no proof that he doesn't do well. We do see him occasionally doing his homework, we know that he excells in gym class, we've seen him translate at least one line from English to Japanese with no problem, and finally when Principal Kuno stole all the test grades Ranma was not worried about them being bad at all until after Principal Kuno made out like they were horrible which implies that either Ranma really doesn't care at all (which is pretty much countered by Ranma's actions) or Ranma generally does well on his tests. It can also be argued that Ranma did not do bad on that test becuase when they were posted on the news Ranma was not upset and if the grade was really bad Ranma would have been upset. Also Mrs. Hinako rarely tries and get Ranma to do better, she instead tries to get Ranma to take school seriously and to conform to what is expected from students. Also we've never seen Ranma in the manga struggling with his school work.

[A.Nonymous]

Actually we have no proof Ranma ate the 16 cm mushroom because we never see it it is just assumed that he ate the 16cm one.

It's too much of a stretch.
I really can't believe that not only didn't he check the mushroom out himself, but Akane was in on the conspiracy and shorted his mushroom. I mean, sure, it's possible, hell, Nabiki could have palmed the real mushroom, but if it had actually happened that way Takahashi would have devoted an issue to it.
I find it much more probable that Ranma is just emotionally imature due to being raised by a complete moron. And Ryoga's in the same boat seing as he was raised by a dog. Akane though was raised by a sister who was only three years older than her...and doesn't live in the same world as everyone else.

[Cyber_Skaarj]

I really can't believe that not only didn't he check the mushroom out himself, but Akane was in on the conspiracy and shorted his mushroom. I mean, sure, it's possible, hell, Nabiki could have palmed the real mushroom, but if it had actually happened that way Takahashi would have devoted an issue to it.

And there's the short of it really. No matter how much we might argue and speculate, Takahashi created Ranma 1/2 and she made Ranma 16. Seeing as how she made it a romantic comedy, I highly doubt she would have included some conspiracy to hide Ranma's true age.

[Alathon]

In response to the original question: Not knowing his actual age, and going by observation, I'd place him around 14.

[MacShimi]

This is a reply to Nekomata-sensei in particular:
Looking at your argument about Takahashi's archetypal roles I think that while I'd like to say that a man hitting a woman is unheard of, I think that in Japan, just as in other parts of the world this is not so. In fact, in Japanese culture, which is still very tolerant of machismo wife-beating is not manly but is tolerated as a social problem (in that it exists, and that there are many cases of it).
Moving on from Nekomata-sensei's post: How many people here would defend a man who constantly beat his fiancée or girlfriend when she upstaged him, revealed his pretensions as egotistical, or used a quick verbal put-down? Not many, especially in the west. Yet there seem to be a large number of people online willing to make excuses for Akane.
Were I to guess at ages for the characters I'd have to say that 16 sounds about right, physically at least. In mental terms the ages of the characters vary widely and also are relative to their areas of expertise. Ranma's maturity in terms of martial arts transcends that of Happosai, and is the equal of Cologne. On the other hand, Ranma's ability to form lasting healthy friendships and social relationships hasn't really advanced since Genma left Ukyo behind and stole her dowry.
Akane is the least mature of her entire family; she acts like a 5 year old. She daydreams constantly about things she wants to do, and engages others in let's pretend scenarios. She is also violent when these pretend games are interrupted. I also note that she is not interested in sex in any way, and regards even reasonable actions (like Ranma's initial meeting) as deliberate perversion despite evidence to the contrary which she had been presented with. So were I to judge Akane on mental age, I'd say 5 years old.
I guess I could go on, but this post is long enough already. I don't want this to be read as flame-bait for those who are fond of Akane, this is intended as a frank and considered statement of opinion. People are welcome to disagree, I'd just like to hear their reasons, not a vociferous denunciation.