Following along with my usual need to know everything about Hogwarts and the wizarding world as a whole, I was giving some serious thought to how big Hogwarts is this weekend.
One one hand, JK was asked this exact question once during an interview and she replied that there were about 1000 students, which you would think would settle the matter. BUT NO, it does not, because I don’t know what books JK was writing, but the books I was reading really only point to there being 250-300 students at Hogwarts. This has been gone over quite a few times before on the internets, but real quick:
There are 5 total Griffyndor boys in Harry’s year (Seamus, Dean, Neville, Ron & Harry himself). Assuming there are an equal number of girls, that puts 10 students per house per year. 40 students per year x 7 years = 280 students; Assuming that there’s some variation (for instance, I can only think of 3 Gryffindor girls in Harry’s year – Lavender, Parvati & Hermione), I feel pretty confident in saying 250-300. Going by JK’s math – 1000 students total is 250 per house, divided by 7 years is ~35 per year total.
Now, JK’s math doesn’t exactly make sense, for a simple reason that she herself included in the books – double classes. Harry & co. are shown repeatedly taking double potions with the Slytherins and double Herbology with the Hufflepuffs. If there are 35 students per house per year, that’s 70 kids – far too many for a single teacher to handle on their own (and there isn’t ever any mention of teacher’s aids or anything like that). 20 students (10 from each House) sounds like a more reasonable number.
Obviously, since this has been discussed on the internet before, so there is a solution that’s been brought up – Harry was born at the end of a war that had been going on for 10 years, and it’s entirely possible that the wizarding birth rate just sharply dropped during that time. So many witches and wizards died young during the war – how many of them were like Gideon and Fabian Prewett, who left behind no children, or James and Lily Potter, who only had one? It seems like an INCREDIBLY steep drop off – nearly a 75% drop, if I’m doing my math right – but I’ve never looked into wartime v. peacetime birthrates in the real world, so I don’t know if it’s possible.
Then, of course, you have the description of the Slytherin vs. Gryffindor quidditch match in Prisonor of Azkaban – it’s described as 200 people dressed in Slytherin green, and they’re (by far) the minority. There isn’t any indication that outsiders are invited to Quidditch matches – and I think we would have a lot more of Mrs Weasley if parents were allowed / encouraged to come to games, after all at one point the team was like 75% her kids – so where did all those people come from? Or are we to believe that the 200 people was Harry’s terrible attempt at estimating, and there are really fewer people by far?
At the end of the day there isn’t really any definitive answer, because any answers we come up with will just raise more questions – if the school has far fewer students than usual when Harry is attending, why aren’t there way too many teachers for the number of students? Did Hogwarts go through a mass firing in the few years before Harry started? – until JK just does the right thing and dedicates her life to writing an exhaustive encyclopedia of all things related to the wizarding world.