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Understanding the difference between annual percentage rate, or APR, and interest rate could save you thousands of dollars on your mortgage. But if you’re like most homebuyers, you probably don’t know that the interest rate and the APR measure two important, but different, costs associated with your home loan.

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Interest rate and APR

The interest rate is the cost of borrowing the principal loan amount. It can be variable or fixed, but it’s always expressed as a percentage.

The APR is a broader measure of the cost of your mortgage because it reflects the interest rate, as well as other costs such as broker fees, discount points and some closing costs. The APR is also expressed as a percentage.

Why have both?

“The main difference is that the interest rate calculates what your actual monthly payment will be,” says Sean O. McGeehan, a mortgage sales manager in Chicago. “The APR calculates the total cost of the loan. A consumer can use one or both to make apples-to-apples comparisons when shopping for loans.”

For example, a loan with a 4 percent rate will have a lower monthly payment than a loan with a 6 percent rate, assuming both are fixed for the same term. Likewise, the total cost of a loan with a 4 percent APR will be less than one with a 6 percent APR.

Where it gets tricky

Separately, the interest rate and the APR have their limits. But together, borrowers should be able to use both figures to determine their monthly payments, as well as their total costs. The trick, says McGeehan, is to understand the interplay between the two figures.

“If a consumer is only focused on getting the lowest monthly payment, they should focus on the interest rate,” McGeehan says. “But if the consumer is focused on the total cost of the loan, then they can use the APR as a tool to compare the total cost of two loans.”

This chart shows the interest rate, APR and total costs over time for a $200,000 mortgage in which 1.5 discount points cut the interest rate by one-quarter of a percentage point, and another 1.5 discount points cut the interest rate by a further quarter of a percentage point.

3 loans, same amounts, 3 APRs
Interest rate 4.5% 4.25% 4%
Discount points 0 1.5 3
Points and fees $2,800 $5,800 $8,800
APR 4.619% 4.492% 4.36%
Monthly payment $1,013 $984 $955
All costs, 3 years $39,281 $41,220 $43,174
All costs, 10 years $124,404 $123,866 $123,380
All costs, 30 years $367,613 $354,197 $343,739

Time horizon matters

If you plan to stay in your home for 30 years or more, it probably makes sense to go with a loan that has the lowest APR because it means you’ll end up paying the lowest amount possible for your house. But if your time horizon isn’t that long, it may make sense to pay fewer upfront fees and get a higher rate — and a higher APR — because the total costs will be less over the first few years.

“Because APR spreads the fees over the course of the entire loan, its value is optimized only if a borrower plans to stay in the home throughout the entire mortgage,” says Gloria Shulman, founder of CenTek Capital Group in Beverly Hills, California.

Figure the break-even point

If you’re planning to stay in your home for a shorter period, you need to do the math and figure out where your break-even point is. Bankrate’s mortgage points calculator will help.

For example, if you chose a 0.25 percent lower rate for an additional 1.5 points because of the lower APR, but you moved in five years, you lost money. Your break-even on the points was seven years.

Unfortunately, those calculations can often be confusing for most homeowners, which is why it’s crucial to pick the right lender.

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