How is simple interest calculated? Interest on simple interest loans accrues daily. Therefore, the portion of your monthly payment allocated to interest may fluctuate. To calculate the interest due on your loan, follow these steps: Obtain the new principal balance of your loan from your online banking account. Multiply your principal balance by your interest rate. Divide that figure by 365 days (366 days in a leap year) to find your daily interest accrual, known as the “per diem”. Multiply the per diem by the number of calendar days elapsed since the date of your last payment. Click here for more details.
