Legal analysis: The calculation method of private lending interest is as follows: 1. Accumulate the daily loan balance according to the actual number of days, and multiply the accumulated product by the daily interest rate to calculate the interest. 2. The determined principal and the agreed interest rate shall be calculated one by one according to the interest calculation formula. The transaction interest method is generally used to calculate the interest of deposits and loans with relatively fixed principal.

Legal basis: Article 680 of the Civil Code of People's Republic of China (PRC) prohibits high-interest lending, and the loan interest rate shall not violate the relevant provisions of the state. If there is no agreement on the payment of interest in the loan contract, it shall be deemed that there is no interest. If the loan contract does not specify the method of interest payment, and the parties cannot reach a supplementary agreement, the interest shall be determined according to the local or the parties' trading methods, trading habits, market interest rates and other factors; Loans between natural persons are regarded as having no interest.