You can add up to 20.
If you want to add more than 20, you will need to remove some of the colleges to add new ones. You can do this in your studentaid.gov account.
Log in to your studentaid.gov account.
Under My Activity, click on your FAFSA® submission. On the Details page, select the Add or Remove Schools button.
If you have a paper Submission Summary, you can replace the colleges listed on the Submission Summary with other colleges and mail it back to the Federal Student Aid Office. Note that the paper Submission Summary only allows you to change up to three schools.
If your FAFSA® form has 20 schools, any new schools you add will replace one or more of the schools already on the list.
Any schools you remove will still have the FAFSA® information you submitted if they were on your original list. When you remove a school, they won’t have access to any new FAFSA® information you provide after you've removed that school.