Both describe what borrowing costs you, but they measure different things.

Your interest rate applies to your loan balance. It's the number that produces your monthly principal and interest payment. APR takes that rate and folds in certain costs of obtaining the loan, expressed annually — which is why it's almost always the higher figure.

Here's where the confusion starts. You cannot calculate a monthly payment from an APR. Many borrowers see the APR and assume that's what they're paying each month. Your payment comes from the note rate. APR exists so that loans with different cost structures can be compared on common ground, and federal rules require it to be disclosed.

Not every cost makes it into APR, either. Lender charges like origination fees, discount points, and certain lender fees are included. Third-party costs — appraisal, title insurance, credit report, recording fees — are largely not. That makes APR a different number from the cash you'll actually bring to closing.

The gap between the two is the signal. A wide gap means meaningful upfront costs; a narrow one means few. Which is better flips entirely depending on how long you keep the loan. Holding long term can justify paying upfront to lower the rate. Selling or refinancing within a few years usually argues the opposite.

APR has limits too. It's calculated assuming you hold the loan to full term, so it misstates what you'll actually experience if you don't. For an ARM, the gap widens further, because the APR estimates post-adjustment rates using assumptions that may not hold. To compare specific offers accurately, read the interest rate and APR together on each Loan Estimate, and check the "In 5 Years" figures on page 3.