① Interest = principal × year (month )× year (month) interest rate

If the interest-bearing period is a whole year (month) and days, the interest-bearing formula is:

② Interest = principal × annual (monthly) × annual (monthly) interest rate+principal × odd days × daily interest rate.

At the same time, banks can choose to convert all interest-bearing periods into actual days to calculate interest, that is, 365 days per year (366 days in leap years), and each month is the actual number of days in the Gregorian calendar of the current month. The interest-bearing formula is as follows:

③ Interest = principal × actual days × daily interest rate

These three formulas are essentially the same, but because the interest rate conversion is only 360 days a year. However, when calculating the actual daily interest rate, it will be calculated according to 365 days a year, and the result will be slightly biased. Which formula is used specifically, the central bank gives financial institutions the right to choose independently. Therefore, the parties and financial institutions can agree on this in the contract.

Extended data:

Influencing factors of annual interest rate

1, central bank policy

Generally speaking, when the central bank expands the money supply, the total supply in loanable funds will increase, the supply exceeds demand, and the natural interest rate will decrease accordingly; On the contrary, the central bank implements a tight monetary policy, reducing the money supply, so that loanable funds's demand exceeds supply, and interest rates will rise accordingly.

2. Price level

Market interest rate is the sum of real interest rate and inflation rate. When the price level rises, the market interest rate also rises accordingly, otherwise the real interest rate may be negative. At the same time, due to rising prices, the public's willingness to deposit will decrease, while the loan demand of industrial and commercial enterprises will increase. The imbalance between deposit and loan caused by loan demand exceeding loan supply will inevitably lead to an increase in interest rates.

3. Stock and bond markets

If the securities market is on the rise, the market interest rate will rise; On the contrary, interest rates are relatively low.

4. International economic situation

Changes in a country's economic parameters, especially changes in exchange rates and interest rates, will also affect interest rate fluctuations in other countries. Naturally, the rise and fall of the international securities market will also bring risks to the interest rates faced by international banking business.

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