APR, APY, and interest rate are three different things

Three numbers get quoted when money is borrowed or saved, they sound interchangeable, and they are not. Comparing the wrong pair is how a worse deal wins.

Interest rate

The base rate charged on the balance, and nothing else. It excludes fees entirely, which makes it the least useful number for comparing offers — and, not coincidentally, the one most prominent in advertising.

APR — annual percentage rate

The interest rate plus the mandatory costs of borrowing, expressed as a yearly rate. On a mortgage that includes origination fees, points, and certain closing costs.

This is why a loan advertised at 6.5% might carry an APR of 6.8%: the gap is the fees, annualised. When comparing loans, compare APR. A lower interest rate with heavy origination fees frequently loses to a higher rate with none.

One caveat: APR spreads fees across the full term. Repay early and you have absorbed those fees over a shorter period, so your true cost was higher than the APR implied. APR is the right comparison tool when you intend to keep the loan.

APY — annual percentage yield

The number for savings, and the one that includes compounding. This is the real difference between the two acronyms: APR describes a rate before compounding, APY after.

A 5% nominal rate compounded monthly produces an effective 5.116%over a year, because each month's interest starts earning too. That is the APY.

So a savings account advertising “5% APY” and one advertising “5% interest, compounded monthly” are not the same offer. The second is better, and only the APY makes that comparable at a glance.

How much compounding frequency actually matters

$10,000 in a 12-month CD at 5%, compounded two different ways:

• Compounded daily — $10,513 at maturity, $513 of interest.
• Compounded annually — $10,500, $500 of interest.

A difference of $13. Real, but small — which is the honest conclusion. Compounding frequency is worth understanding and rarely worth agonising over. The rate itself, and the fees, dominate.

The number that is not a rate at all

Total cost deserves more attention than it gets. A $25,000 loan at 7% over five years costs $495 a month and $4,702 in interest — $29,702 all in.

Stretch the same loan over seven years and the monthly payment falls, which feels like winning, while total interest rises. Lenders and dealers negotiate on the monthly payment for exactly this reason. It is the number that can be improved while the deal gets worse.

Reading an offer properly

Borrowing: compare APR, not the interest rate. Then check total cost across the full term, and be suspicious of any conversation conducted purely in monthly payments.

Saving: compare APY, which already includes compounding. Then check for the conditions attached — introductory rates that expire, minimum balances, caps on the balance that earns the headline rate.

Credit cards: note that a single card carries several APRs — purchases, balance transfers, and cash advances are usually charged differently, and cash advances typically start accruing immediately with no grace period.

None of this is complicated once the three words are separated. The confusion is not accidental, and the defence is simply knowing which number answers which question.