I am a sophomore in high school, and I have been looking into the SAT’s recently. What I know about them is the general SAT, which is scored out of 2400 and colleges give a big importance to. I have stumbled across the subject SAT’s and I am very unfamiliar with them. Are there a certain amount you need to take? If so, which ones are more recommended, and what do they consist of? How long are they, and what are they scored out of? Please help soon! Thanks!!
No, most colleges do not require any SAT Subject Tests, with the exception of a few that might require a math or english test. They are scored out of 800 and take 60 Minutes to complete. You should take them if you’re good at a certain subject that they’re offered in. For example, I excel in biology so I will be taking the SAT Subject Test Biology E/M. They are offered in a wide range of topics (which you can find on the college board’s website). They look good to colleges and can sometimes test you out of a beginning class for that topic, for example: introductory college biology. Hope this helped. 
Thank you so much! This really helped!
You should look into what the schools you’re applying to require or recommend, though. Most of the ivy league recommends two subject tests. (I think only a few schools, like Georgetown, recommend three.) Most state schools won’t ask for them at all.
There’re a lot of fantastic resources in the SAT forum, if you want more in-depth info on each of the sections/subject tests. You might also want to consider the ACT, in case you decide the SAT is not for you.
The top 30 or so colleges in the us require normally 2 subject tests in addition to act or sat. Georgetown “recommends” three. About 10 of these 30 will accept act with writing in lieu of subject tests. Scoring well on subject tests is important at the schools that require them. You would normally take math I or math ii and other topics. It is good you are thinking about this now as scheduling these tests can be tough- you can’t take sat and subject tests on same test date. Easiest thing to do is to take them after completing related ASAP course although material is not identical to what’s covered in the AP. Score distribution varies quite a bit from one subject test to another