how big does something need to be to be considered a kaiju

This actually a really cool question.

Now, im not sure if its because my copy of GMK sucks in the subbing department, but in that movie it stated Baragon to be about thirty meters tall. That would make him even smaller than Zilla at 55-60 meters tall. And his length would most likely be 60-70 meters long.

In the Showa series Baragon is only 25 meters.

Well not to be a spoilsport, but the Kaiju we commonly know as Kaiju are actually daikaiju.

Kaiju can be just about any size really, though most smaller, more 'realistic' ones are usually refered to as Kaibutsu, humanoid ones are refered to as Kaijin.

But in the end, it still just means mysterious/creature/beast/animal/human/thing.

I think "kaiju" has taken on a specific idea amongst english speaking fans. Just like "tokusatsu" literally means "special technique," but is often translated as "special effects," the word is usually used to refer to a specific [iconic] style of Japanese special effects cinema.

Likewise, "kaiju" is now an encompassing word for the Japanese giant monster. While not literally accurate, it has become the standard to refer to these giant creatures as.

GMAN2887

I agree completely, but OP was basically asking for technical explenations, thus I gave one.

Personally I'd say anything about 20ft or so-- as I've heard the word Kaiju used to describe creatures that 'small'-- and I hate using the word small when refering to 20ft monsters.

Either way, I'd say what warrants being a kaiju, from American expectation, is the general japanese spirit behind the monster.

I.E. Pacific Rim's homage to anime and tokusatsu. So it doesn't have to inheretly be Japanese to be a kaiju I guess, but if we are splitting hairs on nerdom termonology, we could be here all night. 

In a more literal sense "kaiju" could be used to describe anything from Frankenstien's monster to Gorgo. But if we're speaking on a level of word choices and references used to label specifics, kaiju does directly refer to Japanese monsters alone. Pacific Rim is tricky because of the script's diction. It directly uses the word "kaiju" as if it's an english term, much in the way the fandom uses it. I'm hesitant to give it a pass simply because it's an homage to tokusatsu, but the fact is the monsters are both called and promoted as "kaiju" so it's hard to get around.

The question is do movies like Yonggary and Gorgo get the pass since they're very, very clearly inspired by the kaiju genre and tokustatsu. Those movies aren't from Japan, yet they wouldn't exist without tokusatsu and daikaiju eiga. I'm fairly lenient about that kind of thing myself, yet it's an interesting question to consider. Tokusatsu isn't specifically a genre, but there needs to be some clear classification as to what these movies are and where they come from.

Kaiju, on the other hand, is often considered a subgenre-- Specifically Japanese movies about giant creatures attacking cities and engaging in battle with others. So where do we draw the line?

No film historian has cleared that up and I've spent the better part of the last year researching an answer. It's not exactly easy.

I'm not sure there needs to be a line honestly.

I think its possible for something to be a kaiju film and something else to be a film with kaiju in it-- if we are speaking about subgenres and such.

Either way, the kaiju subgenre of tokusatsu is sadly pretty sparce and almost dead (Stave for the obligatory Ultraman blurb to pop up occassionally, though I'd consider Ultraman to be a part of the 'giant hero' genre more than the kaiju genre, but that is  just me).

I think at the end of the day, its all pretty subjective. 

Interesting comment about the difference between a kaiju film and a film with kaiju in it. In that case, what makes a kaiju a kaiju? And if a film doesn't necessarily have to be of the kaiju genre to star a kaiju, then there must be a strict definition, must there not?

I think it is important to look into, find lines and define becuase the tokusatsu genre is dying. With Super Sentai, Kamen Rider and Ultraman (which is practically on life support) being the reminants of a style/genre that brought Japanese cinema back from the brink, I feel like the definition of this style will be lost in time and harder to define in the future.

Just because it's dying doesn't mean it has to fade into obscurity and finding more strict definitions can help perserve it in film history.

At least 40 metres tall and 500 tonnes.

Well, the word "Kaiju" means "strange beast" it never mentions the size or attributes to make it a kaiju.  The beast in Half-Human is conidered a Kaiju and he's not that big at all.

That depends, do you thing the HOST is a Kaiju? I'm on the fence with that one. I would say they have to be about the size of a city bus. 

Kaijugroupie84 is on the ball with this one.  Kaiju means "strange beast", so (no matter what Zilla might have to say), size may not matter all that much!  Not including baby kaiju, Toho's smallest full blown kaiju is probably the Destroy All Monsters version of Varan, who comes up to only 10 meters in height and weighs only 60 tons.  Heck, Godzillasaurus is bigger than that!

i think someone already said it, but kaiju means "strange beast". So anything that's strange and a beast is considered a kaiju. I think the word you are thinking of is "DAIKAIJU", which is denoted to a large monster, such as Godzilla. And because the word "large" is a very subjective term, it can really range anywhere from two inches to twenty million kajillion trillion miles tall.

but for the sake of giving you an answer..

I'd say 15 meters or higher.

when i said kaiju, i just meant the big ones that we are all used to seeing, but that was some cool info with the definitions and all

I think he means a Daikaiju. Not a kaiju...

25-30 metres and maybe only 40 tons. Because if we take the mass in consideration...Godzilla's bones would break or any other big Kaiju.