Interest Rate Converter

When Do You Need to Convert Interest Rates?

You see a financial product with an annual yield of 4.2%, paid monthly, and want to know how much interest you'll actually receive each month? Or you took out a loan with a monthly interest rate of 0.5% in the contract and want to calculate if the annual rate complies with regulations? This tool helps you solve these problems—converting annual interest rates, monthly interest rates, and daily interest rates according to your chosen conversion rules.

Principles and Formulas

There are two main algorithms for interest rate conversion:

• Simple Interest (Single Interest): Divide proportionally by month or day. Formula: Monthly Rate = Annual Rate ÷ 12; Daily Rate = Annual Rate ÷ 360 (or 365). Commonly used for credit card cash advances and short-term loans with daily interest calculations.
• Compound Interest Rate (Effective Annual Rate): Considers reinvestment of interest. Formula: Monthly Rate = (1 + Annual Rate)^(1/12) - 1; Daily Rate = (1 + Annual Rate)^(1/365) - 1. Commonly used for bank wealth management products and annual rate conversions in equal principal and interest repayment calculations.

Our calculator defaults to simple interest mode (360 days a year, 30 days a month). You can also switch to "Compound Interest Mode" to use the industry-standard effective annual rate conversion.

How to Use

1. At the top of the calculator, select the interest rate type you know: annual rate, monthly rate, or daily rate.
2. Enter the number in the corresponding input box, for example, enter "6" for the annual rate.
3. Select the target type you want to convert to: monthly rate or daily rate? Click the corresponding button.
4. If you need to calculate using compound interest, check "Compound Interest Mode".
5. The result will be displayed immediately below: Monthly Rate = 0.5%, Daily Rate = 0.0167% (using simple interest, one year = 360 days).

Complete Example: Converting 6% Annual Rate to Monthly and Daily Rates

Scenario: A loan with an annual interest rate of 6%, and you want to know the monthly and daily interest rates.

Simple Interest Method:

• Monthly Rate = 6% ÷ 12 = 0.5%
• Daily Rate = 6% ÷ 360 = 0.01667%

Compound Interest Mode (Effective Annual Rate):

• Monthly Rate = (1+0.06)^(1/12) - 1 = 1.004867 - 1 = 0.4867%
• Daily Rate = (1+0.06)^(1/365) - 1 = 1.000159 - 1 = 0.0159%

Interpretation of Results: Under simple interest, a monthly rate of 0.5% appears higher than the 0.4867% under compound interest because simple interest does not account for compounding effects. The difference in daily rates is small, but the long-term cumulative impact is significant.

Reverse Example: Deriving Annual Rate from 0.5% Monthly Rate

In the calculator, select "Monthly Rate", enter 0.5, and click "Convert to Annual Rate". In simple mode, Annual Rate = 0.5% × 12 = 6%. In compound mode, Annual Rate = (1+0.005)^12 - 1 = 1.061677 - 1 = 6.1678%. Comparing the two, you'll find that the compound interest conversion results in a higher annual rate—this is because interest is earned on interest each month.

How to Interpret the Results

Typical Use Cases

• Mortgage Rate Comparison: You receive a bank pitch saying "monthly payment rate 0.35%", use the calculator to convert to an annual rate of 4.2%, then compare it with the market's LPR plus basis points to decide whether to take the loan.
• Credit Card Daily Interest Calculation: Credit card cash advance daily rate is one ten-thousandth (0.05%), converted to annual rate = 0.05% × 360 = 18%, far exceeding regular loans, reminding yourself to avoid cash advances.
• Wealth Management Yield Conversion: A money market fund with daily interest accrual has a 7-day annualized return of 2.2%, and you want to know the daily actual return: Daily Rate = 2.2% ÷ 365 ≈ 0.00603%, about 0.603 yuan per day per 10,000 yuan.

Important Notes

• Our calculator defaults to 360 days a year and 30 days a month (simple interest). If your actual business uses 365-day interest calculations (such as bonds), please manually switch to the "365 days" option or adjust accordingly.
• Compound interest mode applies to continuous or periodic compounding scenarios, but the actual interest rate for equal principal and interest loans requires IRR calculation, and this tool does not replace loan IRR calculations.
• Simple interest and compound interest conversion results may differ. Financial contracts typically specify whether it is an "annual interest rate" or "annualized yield". Please choose the conversion method according to the contract terms.

Common Misuses

1. Confusing Simple Interest with Compound Interest: Using simple division to calculate daily rates from an investment product's annualized yield, ignoring compounding effects, leading to overestimated returns.
2. Getting the Number of Days in a Year Wrong: Daily Rate = Annual Rate ÷ 365, but using 360 instead, causing calculation errors (e.g., bonds commonly use 365, banks commonly use 360).
3. Directly Multiplying Monthly Rate by 12 as the Annual Rate: If monthly interest is calculated using compounding (such as monthly compounding), the actual annual rate should use (1+Monthly Rate)^12-1, not simple multiplication by 12.
4. Ignoring Interest Accrual Periods: Daily Rate × Actual Days ≠ Annual Rate (because the number of days is not fixed), conversion must be based on the agreed annual base days.

Frequently Asked Questions (FAQ)

1. If the annual rate is 6%, what is the daily rate?
Simple Interest: 6% ÷ 360 = 0.01667%; Compound Interest: approximately 0.0159%. It depends on whether you consider compound interest and the number of days in a year.

2. If the monthly rate is 0.5%, is the annual rate 6% or 6.17%?
If it is simple interest, Annual Rate = 0.5% × 12 = 6%; if you consider compound interest (monthly compounding), it is (1+0.005)^12-1 ≈ 6.17%. Please choose based on your business scenario.

3. Does this calculator support effective annual rate (EAR) conversion?
Yes. Switch to "Compound Interest Mode" to use the effective annual rate formula, applicable to wealth management products, loans, and other scenarios requiring compound interest conversion.

4. Why is my calculated daily rate different from the bank's?
Banks may use 360 or 365 days, and may also use compound interest. Please check which interest calculation method your business uses, then select the corresponding days or compound interest mode in the calculator.

5. Is a daily rate of one ten-thousandth (0.05%) considered usurious?
Converting daily rate 0.05% to annual rate: 0.05% × 360 = 18% (simple interest), or (1+0.0005)^365-1 ≈ 19.56% (compound interest). The current legal protection limit is 4 times the LPR (approximately 14%-15%), so exceeding this may not be protected by law.

Now you can try your own numbers in the calculator above—enter a known rate and get all other forms of rates with one click.