this seems to be a hard question, with some claims of 50,000 kanji. i guess if i limit the kanji to ones that have on-yomi, then i will have a list of kanji that japanese actually have used. i'm guessing this is about 6000. i don't think there are 50,000 characters with on-yomi. i dont expect to find any answer to my question but i just figured i'd ask and might get lucky.

Well.. i'm not pro at knowledge of kanji, but almost each kanji got kunyoumi and onyoumi, so you have to learn each of them, but not all of them, also, you dont have to learn all 50 000 kanji, but, i think, that avrenge japanese know about 2000 or 3000 kanji,(with many on/kunyoumi). So, try not to hang your self, while learning them!
X_X

Almost all kanji used in Japanese have onyomi. If by kanji you mean hanzi as well (this is what the characters are called when they are used in writing Chinese), that 50,000 figure still seems pretty high-- I have heard estimates more like 20 or 25 thousand. But even in Chinese, not nearly that many have been used at any given time in history.

In Japanese, one has to know the 2000 or so jouyou (general use) kanji for minimal literacy, although if one knows the first 1000 or so (taught in the first six grades in Japanese schools), one can read something like 85% of the words other than names in a typical newspaper article. A college-educated person in Japan may know somewhere around 3000 to 3500 kanji.

In Chinese, the number of hanzi one has to know for minimal literacy is also somewhere around 2000, although many of them are different from the jouyou kanji. Since all words are written with hanzi in Chinese, however, it is more important to know a larger number.

Only scholars and language specialists are likely to know tens of thousands of characters.