This calculation method assumes that each month has 30 days and a year has 360 days. It is frequently employed in the realm of mortgage calculations and certain types of short-term lending. As an example, if an annual interest rate is applied to a principal amount, the daily interest rate is determined by dividing the annual rate by 360. This daily rate is then multiplied by 30 to arrive at the monthly interest amount.
This system provides a simplified approach to interest accrual, offering ease of computation, particularly in the pre-digital age. Historically, this simplification aided manual calculations, particularly when precision was less critical than speed. However, it is important to recognize that this method can result in a slightly higher interest charge compared to calculations that account for the actual number of days in a month or year.