According to the information you provided, suppose you borrowed 1 10,000 yuan from the Internet and paid it back to 900 yuan every month. To calculate interest, you need to know the interest rate, repayment period and repayment method of the loan. The following are the general principles of interest calculation:

1. Determine the loan term: You didn't mention the loan term. Assuming the loan term is 12 months, the monthly repayment amount is 900 yuan.

2. Determine the repayment method: there are usually two ways: equal principal and interest and average capital. Matching principal and interest means that the monthly repayment amount is the same, but the interest gradually decreases and the principal gradually increases; Average capital refers to the monthly repayment of the principal unchanged, but the interest gradually decreases. As you have not provided the repayment method, we cannot accurately calculate the interest.

3. Calculation of total interest: Assuming equal repayment of principal and interest, the total interest can be calculated as follows:

-First, determine the annual interest rate. Suppose the annual interest rate is 10%.

-Calculate the monthly interest rate. Monthly interest rate = annual interest rate/12 =10%/12 = 0.83%.

-Calculate the number of repayment periods. Suppose the term is 12 months and the number of repayment periods is 12.

-Calculate monthly interest using the following formula: monthly interest = current loan balance × monthly interest rate.

-Calculate the total interest using the following formula: Total interest = sum of monthly interest.

-For example, in the first month of repayment, total interest = current loan balance × monthly interest rate; In the second month of repayment, the total interest = (current loan balance-monthly repayment amount) × monthly interest rate, and so on.

Summary:

To accurately calculate the loan interest, we need more detailed information, such as loan interest rate, repayment period, repayment method and so on. According to the information you provided, we made some assumptions and provided an example of calculation method. Please contact the lending institution for accurate interest calculation information. Remember, loan interest may also be affected by other factors, such as liquidated damages and deferred repayment fees.

Extended data:

1. The loan interest rate is usually affected by many factors, such as the borrower's credit rating, loan amount and loan purpose.

2. Different countries or regions may have different ways to supervise loans and calculate interest. Please calculate the interest accurately according to local laws and regulations.

3. Before the loan, it is recommended to know all the terms in the loan contract in detail, including interest rate and repayment method.