The annual effective interest rate is the actual return on a savings account or any interest-bearing investment when the effects of compounding over time are taken into account. The nominal interest rate does not reflect the effects of compound interest or the commissions that these financial products entail. Let's see how we can learn how the effective annual interest rate works.
What is the effective annual interest rate?o
The annual effective interest rate is the actual return on a savings account or any interest-bearing investment when the effects of compounding over time are taken into account. It also reflects the actual percentage owed in interest on a loan, credit card or any other debt. It is also called the effective interest rate, effective rate or equivalent annual rate (APR).
What is the effective annual interest rate for?
A certificate of deposit (CD), savings account, or loan offer may be advertised with its nominal interest rate as well as its annual effective interest rate. The nominal interest rate does not reflect the effects of compound interest or the commissions that these financial products entail. The annual effective interest rate is the real profitability. That is why the annual effective interest rate is an important financial concept to understand. You will only be able to accurately compare multiple offers if you know the effective annual interest rate for each of them.
Formula for calculating the effective annual interest rate
Although it can be done by hand, most investors use a financial calculator, spreadsheet, or online program. Additionally, investment websites and other financial resources regularly publish the effective annual interest rate on a loan or investment. This figure is also usually included in the prospectus and marketing documents prepared by security issuers. The following formula is used to calculate the annual effective interest rate:
Formula for calculating the effective annual interest rate.
Example of using the effective annual interest rate
Let's give an example to better understand how to apply the effective annual interest rate. Suppose we have two investments:
- Investment A pays 10% interest compounded monthly.
- On the other hand, a B investment pays 10,1% compounded semiannually.
So, which of the two investments is better? In both cases, the announced interest rate is the nominal interest rate. The annual effective interest rate is calculated by adjusting the nominal interest rate to the number of capitalization periods that the financial product will experience in a period of time. In this case, that period is one year. The formula and calculations are as follows:
- For investment A, it would be: (1 + (10% ÷ 12)) ^ 12 – 1 = 10.47%
- For investment B, it would be: (1 + (10.1% ÷ 2)) ^ 2 – 1 = 10.36%
Investment B has a higher stated nominal interest rate, but the annual effective interest rate is lower than the effective rate of Investment A. This is because Investment B compounds fewer times throughout the year. If we invest, for example, 5 million euros in one of these investments, a wrong decision would cost us more than 5.800 euros per year.