Is the SoFi rate simple or compounded? December 30, 2020 18:25 Updated Follow Simple. The interest is calculated based on the principal amount of the loan. Related articles How is my interest calculated on my SoFi loan? How often is the interest accrued and compounded? Why is my loan APR different than my interest rate? What happens if my Personal Loan payment made is more than what I owe? How are payments allocated? What is personal cyber insurance?