APR vs APY: What the Letters Mean and Why Banks Pick Sides

One letter, opposite jobs

APR is the cost-of-borrowing number. Credit cards, mortgages, auto loans and personal loans all quote APR, and by law lenders must disclose it so you can compare. A 24 percent APR credit card and a 7 percent APR auto loan are directly comparable as yearly borrowing costs.

APY is the earnings number. Savings accounts, CDs and money market accounts quote APY because it shows what your deposit actually grows to after a year of compounding. A 4.5 percent APY account turns $10,000 into $10,450.

The one-letter difference is worth memorizing: APR is what you pay, APY is what you earn. If you see APY on a loan or APR on a savings account, slow down, because someone may be showing you the wrong number on purpose.

The math that separates them

Start with a 5 percent rate compounded monthly. Each month the balance grows by 5/12 percent, about 0.4167 percent. After 12 months of growth-on-growth, $10,000 becomes $10,000 times (1 + 0.05/12)^12, which is $10,511.62.

That is a true yearly gain of 5.116 percent. So 5 percent APR with monthly compounding equals 5.116 percent APY. The extra $11.62 is the interest earned on interest during the year.

Compound daily instead of monthly and the APY rises to about 5.127 percent. Compound once a year and APR equals APY exactly. The more frequent the compounding, the wider the gap, which is why the distinction matters most on credit cards that compound daily.

Banks sometimes quote investment products with continuous compounding in the fine print. The math uses the constant e, and the APY becomes e raised to the rate, minus 1. At 5 percent that is 5.127 percent, nearly identical to daily compounding. For everyday decisions, monthly versus daily is the only distinction that matters.

Why each side advertises the flattering number

Banks advertising savings accounts quote APY because it is the bigger number: 5.12 percent APY sounds better than 5 percent interest. Every bank does this, so comparisons between savings accounts are still fair, as long as you compare APY to APY.

Lenders advertising loans quote APR because it is the smaller number. A credit card at 24 percent APR actually costs about 26.8 percent APY with daily compounding, but you will never see that number in the ad.

The takeaway: always compare like with like. Savings against savings means APY versus APY. Loans against loans means APR versus APR, and for mortgages, the APR that includes fees, which we will get to.

Credit cards: APR in action

Credit card APRs look abstract until you translate them monthly. A 24 percent APR means about 2 percent per month. On a $3,000 balance, the first month's interest alone is about $60.

If you pay only the $60 minimum, the balance never shrinks. You have paid $60 for the privilege of owing $3,000 for another month. This is how minimum payments stretch a $3,000 purchase into years of payments and hundreds in interest.

Pay $150 a month instead and the same balance clears in about two years with roughly $800 in total interest. The APR did not change; the payment did. With revolving debt, your payment size matters more than the rate.

Balance transfer offers exploit APR confusion. A card offering 0 percent for 18 months with a 3 percent transfer fee is really charging about 2 percent APR annualized on the transferred amount, still far cheaper than 24 percent. But new purchases on that card often accrue interest immediately, a trap buried in the terms.

Mortgages: APR includes the fees

Mortgage shopping has a twist: the APR on a loan estimate includes most lender fees, while the note rate does not. A $300,000 loan at a 6.5 percent note rate with $8,000 in lender fees might show an APR of about 6.7 percent.

That higher APR is the truer yearly cost, because the fees are real money you pay to get the loan. When two lenders offer the same note rate, the one with the lower APR is charging you less in fees.

But APR assumes you keep the loan for the full term. If you will sell or refinance in five years, upfront fees hurt more than the APR suggests, because you pay them in full but only enjoy the rate for a few years. Match the comparison to your real timeline.

Adjustable-rate mortgages add another wrinkle: the APR is calculated assuming the initial rate lasts, then adjusts according to the index. Since nobody knows future rates, ARM APRs are educated guesses. Compare the initial rate, the caps and the margin separately rather than trusting the blended APR.

Comparing offers the right way

For savings: compare APY, then check compounding frequency and minimum balance games. Two accounts at 4.5 percent APY are equal earners even if one compounds daily and the other monthly.

For loans: compare APR including fees, confirm the compounding frequency, and run the total interest over your realistic timeline, not just the full term.

And never compare a loan's APR directly with a savings account's APY as if they were the same sport. Borrowing at 7 percent APR while earning 4.5 percent APY means your money costs more than it earns, which is exactly why carrying debt while holding savings is usually a losing trade.

One final comparison trick: convert everything to dollars per year. A 1 percent APR difference on a $300,000 mortgage is about $3,000 in the first year. On a $5,000 savings balance, a 1 percent APY difference is $50. Percentages hide scale; dollars reveal it. Teaser rates deserve special suspicion. A credit card offering 0 percent for 12 months then 29.99 percent is not a 0 percent card; it is a 30 percent card with a one-year delay. Always underwrite the go-to rate, because that is the rate you will actually live with.

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