Is the SoFi rate simple or compounded? December 30, 2020 18:25 Updated Simple. The interest is calculated based on the principal amount of the loan. Related articles If I want to payoff my SoFi loan early, can I do so? Why is my loan APR different than my interest rate? Are there any prepayment penalties for paying off my loan early and/or making additional payments? What is the timeframe for funding my Student Loan? How will funds be disbursed? Why did the amount I requested to borrow on my loan change?