APR vs. APY: What's the Difference and Why Does It Matter?

US + UK context APR and APY are terms you will see most often in the United States, where disclosure rules require them. The underlying ideas travel everywhere; in the UK, for example, savings accounts quote an equivalent figure called the AER.

APR and APY look almost identical — three letters apart by a single vowel — and they are easy to mix up. But they sit on opposite sides of a financial transaction. One tells you what borrowing costs. The other tells you what saving earns. Confusing them can lead you to overestimate what a savings account pays, or underestimate what a loan really costs.

The good news is that once you see the single idea that separates them — compounding — the difference becomes clear and stays clear. This guide walks through both, with numbers you can follow on a calculator.

Two words, two sides of a deal

Here is the quickest way to keep them straight. APR — annual percentage rate — usually describes the cost of borrowing. APY — annual percentage yield — usually describes the return on saving. When money is flowing away from you (a loan, a credit card), think APR. When money is flowing toward you (a savings account, a certificate of deposit), think APY.

That is the practical rule. The interesting part is why two different measures exist at all, and the answer comes down to how each one treats compounding.

What APR means

APR expresses the yearly cost of borrowing as a percentage. Its usefulness is that it can capture more than just the raw interest rate — depending on the product, it may also include certain fees rolled into the cost of the loan. That makes it a broader, more honest measure of what credit costs than the headline interest rate alone.

You will encounter APR on credit cards, mortgages, car loans, and personal loans. Because it is meant to standardise how lenders present their pricing, it lets you line up two offers and compare them on something closer to equal footing.

What APY means

APY expresses how much a deposit earns in a year as a percentage, and its defining feature is that it accounts for compounding — the effect of earning interest on interest already paid. Because it bakes in compounding, APY reflects what you would actually earn over a year, not just the advertised base rate.

You will see APY on savings accounts, money market accounts, and certificates of deposit. When two savings products list different APYs, the higher one earns more over a year on the same balance, all else equal.

Interest rate vs. APR

People often treat "interest rate" and "APR" as synonyms, but on a loan they can differ. The interest rate is the cost of borrowing the principal by itself. The APR can be larger because it also reflects certain fees, expressed as a yearly percentage.

Imagine a $10,000 personal loan advertised at a 6% interest rate, but with $300 in upfront fees. The interest rate is 6%, yet the APR will be somewhat higher, because those fees are folded into the annualised cost. This is exactly why comparing APRs — rather than interest rates — gives you a fairer read on which loan is genuinely cheaper.

Compounding: the engine behind APY

Compounding is the single idea that separates a nominal rate from APY. When an account compounds, the interest you earn is added to your balance, and the next round of interest is calculated on that slightly larger balance. Do this repeatedly through the year and you earn a little more than the stated rate would suggest.

The frequency matters. An account can compound annually, quarterly, monthly, or daily. The more often it compounds, the higher the APY climbs above the nominal rate. If an account compounds only once a year, the APY and the stated rate are identical — there is no interest-on-interest yet to capture.

A worked example

Suppose you deposit $10,000 in a savings account with a stated interest rate of 5%. What you actually earn over a year depends on how often it compounds.

The stated rate is 5% in every row, yet the money earned rises with more frequent compounding. That extra earning is precisely what APY captures and the nominal rate hides. It is not a huge sum on $10,000 in a single year, but the same mechanism becomes powerful over long periods — the idea at the heart of how compound interest works.

Now flip to borrowing. A credit card with a 24% APR works out to roughly 2% a month (24% ÷ 12). Carry a $1,000 balance and you are looking at about $20 of interest in the first month alone — and because card interest often compounds, the true yearly cost can edge slightly above the stated 24%.

When you are borrowing

As a borrower, your goal is to pay as little as possible for the money, so you want the lowest APR. Compare APRs across offers rather than interest rates, since the APR is more likely to reflect fees. And remember that on revolving debt like credit cards, the fastest way to avoid interest altogether is to pay the balance in full — no rate, however low, beats not carrying a balance. If card debt is the issue, our guide on getting out of credit-card debt goes deeper.

When you are saving

As a saver, you want the highest APY, because that is the figure that already accounts for compounding and therefore reflects real annual earnings. When you shop for a place to park cash — say, the savings you have set aside in your emergency fund — comparing APYs lets you judge two accounts fairly even when they compound on different schedules.

Common mistakes

• Comparing an APR to an APY. They are not like-for-like. Compare APR to APR, and APY to APY.
• Assuming the interest rate equals the APR on a loan. Fees can push the APR above the rate, so the rate alone can understate the cost.
• Ignoring compounding frequency on savings. Two accounts with the same nominal rate can pay different amounts; the APY is what settles it.
• Focusing only on the headline number on a card. A low APR still costs you if you carry a balance month after month.

The bottom line

APR and APY answer two different questions: what does this cost me to borrow, and what does this earn me to save? APR is the borrower's number and should be as low as possible; APY is the saver's number and should be as high as possible. The reason they diverge is compounding — APY reflects it, while the nominal rate and (typically) a card's APR do not. Keep that one distinction in mind and you will read the fine print on both loans and savings accounts with a lot more confidence.

Frequently asked questions

Sources & further reading

Our explanations and examples are our own. For authoritative definitions and consumer guidance on how these rates are disclosed, these official resources are good starting points: