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APR Vs. APY: What’s The Difference And How Do They Affect Your Mortgage?

Ashley Kilroy5-minute read

August 30, 2021


It’s easy to confuse APR (annual percentage rate) and APY (annual percentage yield). They sound the same, and both involve interest. But be careful; they aren’t interchangeable. Knowing the difference can help you manage your money and make you a wiser borrower. With that in mind, here are some of the key differences between APR and APY.

What Are APR And APY?

Although the two terms look similar, there is a difference between APR and APY. APY calculates the annual cost of a loan and measures how frequently interest will compound. Therefore, you’ll know how much interest is being added to the balance. Although APR accounts for a loan’s combined interest and fees, it does not factor in compound interest.  

The Major Difference: Compound Interest

Compound interest is calculated on a loan or deposit using two factors: the principal balance and the accumulated interest from previous periods. So, it’s earned on top of existing interest.

Here is the formula to calculate how much you’ll make using compound interest:

B = P x (1 + R/N)(N x T)

  • B: Ending balance, including the future value of the investment or loan and interest
  • P: Initial principal
  • R: Annual interest rate in decimal form
  • N: Number of times the interest on an investment or loan compounds in a year
  • T: Length of time you’ll have the investment or loan

Let’s say you deposit $6,500 into a savings account. There is an annual interest rate of 3%, and it’s compounded monthly for 4 years. If we put those values into the formula, we get:

$6,500 x (1 + .03/12)(12 x 4)

After four years, you’d have $7,327.63.

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Calculating And Converting APR And APY

APR and APY are important calculations when you are shopping for loans. Knowing how an APR and APY are calculated can be vital to shopping for a mortgage.

If you want to check your possible mortgage payment, you can also use a mortgage calculator.

Calculating APR

You’ll need to know the expected fees and interests on a possible loan to calculate the APR.

Once you have those two numbers, you can begin:

  1. First, take the fees and total interest you will need to pay over the course of the loan. Add them together.
  2. Divide the sum of those two numbers by the loan principal.
  3. Take step 2’s result and divide it by the loan term’s total days.
  4. Once you have step 3’s answer, multiply it by 365.
  5. Multiply step 4’s answer by 100 to convert the APR into a percentage.

[((Fees + Total interest / Loan Amount) / Loan Term’s Total Days) x 365 ] x 100 = APR

Here is an example calculation:

  1. $400 in interest + $60 = $460
  2. $460 / a principal of $3,900 = 0.11794872
  3. 11794872 / a term of 200 days = 0.00058974
  4. 00058974 x 365 = 0.215
  5. 215 x 100 = APR of 21.5%

Knowing a loan’s APR is helpful for certain borrowers. Since APR includes the high closing costs a mortgage can involve, it can paint a more accurate picture for those looking in this area.

Calculating APY

You can use this formula to find a loan’s APY:

APY = (1 + r/n)n – 1

The r is your interest rate in decimal form. The n is equal to the number of times your investment compounds in a year. For example, let’s say you have an interest rate of 0.05%, and the investment compounds monthly.

APY = (1 + 0.0005/12)12 – 1

Here, APY = 0.050011%

Since APY is applied in situations where your investment is growing, you’ll want to know how to calculate APY. It will help you figure out how much money you are earning over the years.

Converting APR And APY

You can already find the APY using the APR value as we saw with its formula where r was the interest rate. You just input the APR into the formula’s r-value.

So, the calculation is: APY = (1 + APR/n)n – 1

You can also use the APY to find the loan’s periodic rate, giving you the APR.

The equivalent formula is: APR = n x (1 + APY)1/n - n

APR, APY And Your Mortgage

Knowing how to use and calculate APR and APY can be helpful for future home buyers. The two values can give you insight into a mortgage’s true price. APR can show you how much a loan might run, including fees like closing costs. In comparison, APY can give you a more accurate measure of the loan’s annual cost since it includes how often the loan is compounded. So, knowing both the APR and APY of your possible loan can help you get the best interest rate by making you an informed borrower. 

Which Is Better: APR Or APY?

Typically, APY is involved in situations where you earn money through interest on investments. In contrast, APR is used by your lenders for scenarios where you pay interest. So, you’ll find them applied in different settings. APR is useful when creditors use various fees, whereas APR can help with comparing compounded loans.

When APR Is Better

APR is a simpler formula than APY since it doesn’t include compound payments. However, there is an exception with mortgages. Their high closing costs are accounted for in APR, so it will give you a more accurate answer.

There are other situations when you may see APR applied, and most of them involve credit, like car loans and credit cards. Certain lending institutions like to use APR as a promotional offer to persuade borrowers. You might have a 0% APR period at the start, but there will be a high-interest fee for any remaining balance once it’s over. Institutions can also decide what fees to include in the APR.

It’s best to get a breakdown of what your APR includes. That way, you can accurately compare it to other options. Generally, the larger the difference between the APR and interest rate, the greater the loan expense.

Keep in mind that your credit score can influence your APR. The lower the score, the higher the APR will be on your loan.

When APY Is Better

APY is most useful when compound interest is involved since it takes that value into account. So, you’ll generally see it when investments come into play.

Financial institutions like banks usually use APY for investment products. This can include CDs and a high yield savings account. The high APY rate can look better to customers and draw them in. However, you want to make sure that you know exactly how the institution is getting that rate so you can choose wisely.

Find out how often the money is compounded. The more frequently interest is adding to the balance, the more money you will be making.

The Bottom Line: Make Informed Mortgage Choices

You want to ensure your interests are protected when you look for the right mortgage. The best method is to inform yourself. When you know how APR, APY, and the true cost of interest data works, you can search for the best option on your terms. If you’re ready to see your loan options, apply for a mortgage or refinance online.

Take the first step toward the right mortgage.

Apply online for expert recommendations with real interest rates and payments.

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Ashley Kilroy

Ashley Kilroy is an experienced financial writer. In addition to being a contributing writer at Rocket Homes, she writes for solo entrepreneurs as well as for Fortune 500 companies. Ashley is a finance graduate of the University of Cincinnati. When she isn’t helping people understand their finances, you may find Ashley cage diving with great whites or on safari in South Africa.