Calculation formula of monthly payment, monthly interest and total interest of the equal principal and interest repayment method:

1, monthly repayment amount = principal * monthly interest rate *( 1+ monthly interest rate) n/[( 1+ monthly interest rate) n- 1]

Where: monthly interest rate = annual interest rate/12, n represents the number of loan months, and n represents the power of n, such as 180, which represents the power of 180 (loans 15 and 180 months). Note: When calculating (1+ monthly interest rate) n- 1, you must first calculate what is in brackets, and then multiply and subtract 1.

2. Monthly interest = (principal * monthly interest rate-monthly repayment amount) *( 1+ monthly interest rate) (n- 1)+ monthly repayment amount.

Where: n stands for the first month.

Or, the current month's interest = the remaining principal of the previous period * the monthly interest rate (the remaining principal should be deducted from the previously repaid principal).

3. Total interest = monthly repayment amount * loan months-principal

When calculating the total interest with this formula, the monthly repayment amount should be kept at least 6 decimal places, otherwise there will be an error within 1 yuan.

The above formula 1 (monthly repayment amount) is widely circulated outside, and banks are also using it. All loan calculators are based on this principle. Formula 2 is calculated by myself after many times (definitely accurate); Equation 3 is easy to understand. I have something to do now, so I can't rehearse for you. You can "ask" questions.