If you are an incoming frosh, we recommend signing up for 12-15 units of coursework in your first quarter. Keep in mind that adjusting to Stanford is at least the equivalent of a 3-unit course, so give yourself some room to breathe! After your first quarter, you can try taking on more if you like. In the long run, most students will want to reach an average of about 15 units per quarter if they seek to graduate in 4 years.
You will need to sign up for at least 12 units by the end of the first day of classes in order to be considered a full-time student. (See Also: What is a Unit?)
The official add/drop deadline is the end of week three. However, while you can drop all the way through the third week, you should attend any classes you might take by the end of the first week of classes. Professors are often very reluctant to allow students to add a class that they have not been attending, and you may have missed work that cannot be made up.
After the third week of classes, your schedule for the quarter is set (the Final Study List deadline is 5pm on Friday of Week 3).
How many classes should you take? It depends. It depends on the classes, it depends on the workload, it depends on your other commitments, it depends on who you are and how you learn. This decision is best finalized after classes start--the ideal approach is to attend more classes than you expect to take, and by the end of Week 1, decide which of those classes make the best combination for you that quarter.
Typically, expect classes of 3-5 units to be main academic classes that can fulfill requirements and count toward a major, while classes of 1-2 units are usually lecture series or athletic classes, with fewer assignments outside class. Students will combine these in an infinite variety of ways.
Generally, you’ll want to take either 3 or 4 main academic classes each quarter, depending on what they are. 1-2 unit courses are excellent ways to explore, but piling up too many can complicate your schedule.
12-15 units is probably ideal for your first quarter. The maximum number of academic units a first-quarter frosh may enroll in is 20 (no exceptions). Students past their first quarter may petition to take 21 or 22 units in certain cases. See your Academic Advising Director or AARC advisor for details.
Cognitive shifting between types of studying/work often shows a better result than focusing in on one kind of learning. And it leads to less burn out. Most students do best with a balanced workload demanding a mix of exams and essays, a mix of reading and problem sets.
Four main academic classes may be nicely balanced among math, Spanish, chemistry, and history, but if you have two essays and two midterms all due in the same week, you might want to tweak something. It's useful to actually write down all the major deadlines on the Quarter-at-a-Glance planner, and then evaluate the commitments you are making.