APY vs Interest Rate: What Is the Difference?

Two numbers, one account

Both figures describe the same account, but they answer different questions. The stated interest rate — sometimes called the nominal rate — is the percentage a bank says it will pay on your balance over a year, before any compounding is taken into account. The annual percentage yield (APY) is the actual growth you would see after one year once compounding is factored in. For the same account, APY is equal to or higher than the stated rate, never lower.

Think of the stated rate as the price tag on a product and APY as the total cost after taxes and fees at the register. They are related, but they are not interchangeable. A savings account that compounds monthly at 4.80% will not end the year at exactly 4.80% growth — the interest earned in January starts earning its own interest in February, and by December that snowball effect has pushed the real annual growth slightly higher.

Why do banks show both? Lending rules in many countries require deposit products to disclose a rate and a yield, and the two numbers serve different readers. The stated rate is simple and easy to grasp. The APY is the honest measure of what you actually earn, which is why it is the number you should use for comparisons and for projections like the ones this site's compound growth calculator produces.

The stated rate is the headline; APY is the ending

Compounding is the reason the two numbers drift apart. The frequency of compounding — annually, quarterly, monthly, or daily — determines how often already-credited interest gets folded back into the balance and begins earning on its own. The more frequently that happens, the wider the gap between the stated rate and the APY.

A simple rule of thumb: the higher the stated rate and the more frequent the compounding, the larger the gap. At a low rate like 0.50% and annual compounding, the two numbers are nearly identical, which is why casual savers can go years without noticing the difference. At rates above 4%, with monthly or daily compounding — which is what most online high-yield savings accounts and money-market accounts use — the gap becomes visible and, over a decade, worth real money.

There is also the question of how the bank pays interest out. Some accounts deposit earned interest into your balance automatically, which lets it compound. Others, like many certificates of deposit, hold the interest inside the product until maturity. Either way, the APY on the disclosure reflects the compounding the product actually offers, assuming you leave the money alone.

Worked example: monthly vs annual compounding

Let's make this concrete with a deposit of $10,000 at a stated rate of 5% per year. The compounding schedule is the only thing we change.

If the account compounds once per year, the math is a single step. After 12 months the balance is:

$10,000 × 1.05 = $10,500

Interest earned: $500. APY: exactly 5.00%.

Now the same $10,000 at the same stated 5%, but compounded monthly. Each month the bank applies one-twelfth of the annual rate, which is about 0.4167%. The running balance looks like this:

• Month 1: $10,000.00 × 1.004167 = $10,041.67
• Month 2: $10,041.67 × 1.004167 = $10,083.51
• Month 3: $10,083.51 × 1.004167 = $10,125.52
• … and so on, each month's interest calculated on the previous month's total …
• Month 12: $10,000 × (1.004167)¹² = $10,511.62

Interest earned: $511.62. APY: 5.116%. That extra $11.62 is the entire payoff of compounding — interest earned on interest that was already credited during the year. Compound it daily instead and the year ends at $10,512.67, an APY of 5.127%.

None of these numbers is a typo. The stated rate stayed at 5% the whole time; only the frequency changed, and the frequency alone moved the annual result by more than $12 on a $10,000 balance. Scale that over a decade and the difference between 5.00% and 5.127% compounding, both quoted at a "5% rate," grows into hundreds of dollars.

APR vs APY: the comparison table

APR (annual percentage rate) is the mirror image of APY and the source of endless confusion, because it sits on the borrowing side of the same coin. The same compounding math that boosts a savings yield also inflates the cost of a loan. Here is the pair of acronyms laid out side by side.

The reason this matters for your everyday finances: when a credit card advertises an 22.99% APR, that is before compounding — interest that is not paid off starts generating its own interest immediately, which is a story covered in detail in how compounding works against debt. When a savings account advertises an APY, the compounding is already inside the number. The two acronyms face opposite directions, and mixing them up is how people overestimate a loan's cost or underestimate an account's growth.

Comparing deposit products with APY

Here is where the APY earns its keep. Suppose two banks both advertise a "4.85% rate." Bank A compounds annually; Bank B compounds daily. A straight comparison of the headline numbers says they are identical, and it is wrong — Bank B's APY is roughly 4.97%, while Bank A's is 4.85%. On a $20,000 balance held for five years, that difference compounds to several hundred dollars, purely from the frequency of compounding.

So the practical habit is simple: compare APYs, not stated rates, whenever you are choosing between savings accounts, money-market accounts, or CDs. The APY already normalizes compounding frequency, which means a number that looks like a footnote actually contains the entire answer.

A couple of fine-print warnings, though. Some banks quote a promotional APY that applies only to the first few months, after which the rate drops. Others require a minimum balance to earn the advertised APY, and falling below it can drop your rate to a fraction of a percent. The APY is trustworthy only if you expect to meet the account's conditions. Also keep in mind that APY assumes you leave the money in place for a full year; if you withdraw early, especially from a CD with an early-withdrawal penalty, the realized return can be far lower than the quoted APY.

The calculator trap: don't double-count compounding

A subtle mistake shows up when people take an APY from a bank's website and type it into a compound interest calculator as the annual rate while also leaving the calculator's compounding frequency set to monthly. The calculator then compounds a rate that already contains compounding — the result overstates the account's growth.

If the number you are entering is an APY, set the compounding frequency in the calculator to 1 (annually). If the number is a stated nominal rate, enter the actual compounding schedule the product uses. Either route produces a correct estimate; mixing the two inflates the projection. For most short-term comparisons the error is small, but it defeats the purpose of precision, and on 20- or 30-year projections the inflation compounds along with everything else.

When in doubt, a bank's customer support can usually confirm whether a quoted figure is the stated rate or the APY — one sentence that removes the whole ambiguity. And if you are estimating an investment return rather than a deposit rate, the logic in choosing an interest-rate assumption walks through which kind of number belongs in the box.

Common questions

Can the APY ever be lower than the stated rate?

No. Because compounding only ever adds to your balance, the APY is always equal to or greater than the stated rate. If you ever see an account advertised with an APY below its stated rate, a fee or condition is almost certainly hiding in the fine print.

Does APY matter for a one-week deposit?

Hardly. APY describes a full year of compounding, so for money held for days or weeks, the compounding effect is negligible and the stated rate and APY are practically equivalent. APY becomes meaningful over months and years.

Should I use APY or the stated rate in a long-term projection?

Use one or the other consistently — never both. The safest approach is to enter the APY and set the calculator's compounding frequency to annual, since the APY already represents the end result of the product's real compounding schedule.