Good question! "Standard" In terms of characters refer to the 常用漢字 which are the -er- "basic" 2160ish (I will try to remember to update with the exact figure; it was expanded in the last 5-10 years) kanji that are the basis to be considered "literate".
To look at it a bit different for Americans (which is the only basis I have; other counties even within English differ), one could think of reading at an X-grade level. Many publications can be around 5th-grade level (though this comes with its own can of worms).
In English, we have 26 letters of the alphabet. I guess we could call it 52 differentiation lower- and upper-case. We could also double that to 104 for cursive. If we're feeling generous, we could add a couple of shorthand signs (such as an & that is more shorthand).
Now, for japanese, in addition to those 104ish, you now have to learn at least 2160ish Chinese characters (and, if you're japanese, all the latin alphabet as described above, but this isn't applicable to those of use whom are native English speakers looking to learn Japanese).
And, until here, we're only talking about the squiggles used to represent sounds. After this, we actually get into things like vocabulary and grammar and registers ( think something like manners.