Credit card interest is calculated based on the outstanding balance and interest rate. Usually, credit card interest is calculated on a daily basis. Daily interest is calculated based on the daily outstanding balance and interest rate, and is then settled on the repayment date.

Let us use an example to understand specifically how credit card interest is calculated. Assume that your credit card bill date is the 10th of each month and the repayment date is the 30th of each month. You spent 1,000 yuan on January 1st and only paid the minimum repayment amount of 100 yuan on January 30th. How will your credit card interest be calculated?

First of all, we need to understand the interest rate of credit card. Suppose your credit card's annual interest rate is 18, then the daily interest rate is 18 divided by 365 days, or five ten thousandths. This means that every day you pay 0.05% interest on the outstanding balance.

From January 1 to January 30, your unpaid balance is 1,000 yuan, so the daily interest is 1,000 yuan multiplied by five ten thousandths, that is, 0.5 yuan per day. Therefore, the interest for the entire month is 0.5 yuan times 30 days, or 15 yuan.

Please note that this is just a simple example. The actual calculation of credit card interest may be more complicated because different consumption dates, repayment dates and interest rates may be involved. In addition, the above example only calculates interest for one month. In actual use, if you fail to repay in full on time, interest will continue to accumulate, increasing your debt burden.

Therefore, when using a credit card, we should try our best to repay the loan in full and on time to avoid unnecessary interest charges. At the same time, we also need to check our credit card statements regularly to understand our consumption and repayment status to ensure our financial health.