APY is the yearly interest rate a bank pays you on a CD, including the effect of compounding

APY stands for Annual Percentage Yield. It tells you how much interest you'll earn on a certificate of deposit over one year, expressed as a percentage of your deposit. If you put $1,000 into a CD with a 4.5% APY, you'll earn roughly $45 in interest over 12 months (before taxes).

The key word is "yield"—APY accounts for how often the bank compounds your interest, meaning it pays interest on the interest you've already earned. A CD with a higher APY will grow your money faster than one with a lower APY, all else being equal.

Banks are required to show you the APY before you open a CD. This makes it easy to compare one CD to another, because you're looking at the same measurement across all of them.

Key Takeaways

  • APY is the total interest you earn in a year, expressed as a percentage, and it includes the effect of compounding.
  • A higher APY means your money grows faster, so comparing APY between CDs helps you choose which one pays more.
  • APY is different from the interest rate itself—APY is always equal to or higher than the rate because it factors in compounding.
  • The APY you see when you open a CD is locked in for the entire term, so a 4.5% APY on a one-year CD will not change if rates drop.

How compounding makes APY different from the interest rate

Banks calculate interest in different ways. Some compound daily, some weekly, some monthly. Compounding means the bank adds the interest you've earned to your balance, and then pays you interest on that larger amount next time.

The interest rate is what the bank pays on your original deposit. The APY is what you actually earn after compounding happens. If a bank compounds interest daily, your APY will be noticeably higher than the stated rate. If it compounds monthly, the difference is smaller.

For example, a CD might have a 4.40% interest rate but a 4.50% APY, because the daily compounding adds a little extra. Banks must show you the APY so you know the real number—the one that matters to your wallet.

Why APY matters when you're comparing CDs

When you're deciding between two CDs, APY is the number to look at. One bank might advertise a 4.75% rate, and another might advertise 4.70%, but once you account for compounding, the second one could actually pay more. Always compare the APY, not the rate.

The difference between a 4.50% APY and a 5.00% APY might seem small, but on a $10,000 CD it adds up to $50 more per year. On larger deposits or longer terms, the gap grows. That's why shopping around for the highest APY is worth your time.

You'll also see APY vary by term length. A six-month CD might pay 4.25% APY, while a two-year CD from the same bank pays 4.75% APY. Banks set these rates based on what they think interest rates will do, so longer terms often (but not always) pay more.

Your APY is locked in for the entire CD term

When you open a CD, the APY you see is the APY you get for the whole time you hold it. If you open a one-year CD at 4.50% APY and interest rates drop to 3.00% the next month, you still earn 4.50%. That's the safety of a CD—you know exactly what you'll make.

The trade-off is that if rates rise, you're stuck with the lower rate. You can't change your mind and move to a higher-paying CD without closing the one you have, which usually costs you an early withdrawal penalty.

How to calculate what you'll actually earn

The APY tells you the percentage, but you can figure out the actual dollar amount. Multiply your deposit by the APY, then multiply by the number of years you're holding the CD.

For a $5,000 CD at 4.50% APY held for one year: $5,000 × 0.045 × 1 = $225 in interest. For a two-year CD at the same rate: $5,000 × 0.045 × 2 = $450. (This is a simplified calculation; the actual amount may be slightly different because of how compounding works, but it's close enough for planning.)

Keep in mind that the interest you earn is taxable income. You'll receive a 1099-INT form from the bank at tax time, and you'll owe federal income tax on that interest. Some states tax it too.

APY changes between banks and over time

Different banks pay different APYs on the same CD term. Online banks typically pay higher APY than brick-and-mortar banks because they have lower overhead costs. Right now, some online banks pay 4.50% to 5.35% APY on one-year CDs, while traditional banks might pay 0.50% to 2.00%.

These rates change constantly. When the Federal Reserve raises or lowers its benchmark rate, banks adjust what they pay on new CDs. If you opened a CD six months ago at 5.00% APY, a new CD today might pay 4.25% or 5.50%—you can't predict which way it will go.

This is why the APY you lock in matters: you're protecting yourself against future rate drops, but you're also giving up the chance to earn more if rates rise.

Frequently Asked Questions

Is APY the same as interest rate?

No. The interest rate is what the bank pays on your deposit. APY is the interest rate plus the effect of compounding. APY is always equal to or higher than the rate, and it's the number that shows what you'll actually earn.

Can the APY on my CD change after I open it?

No. Once you open a CD, the APY is locked in for the entire term. It will not change if interest rates rise or fall. When your CD matures, you can open a new one at whatever the current APY is at that time.

Why do different banks offer different APYs for the same CD term?

Banks set their own rates based on their costs, competition, and business strategy. Online banks usually pay higher APY because they spend less on branches and staff. Shopping around is the only way to find the best rate for your situation.

How often does the bank compound interest on a CD?

It depends on the bank. Most compound daily or monthly. The bank will tell you the compounding frequency when you open the CD. Daily compounding results in a slightly higher APY than monthly compounding, all else being equal.

What happens to my APY if I withdraw money early?

Your APY doesn't change, but you'll owe an early withdrawal penalty. The penalty is usually a certain number of months of interest. You'll lose some or all of the interest you earned, which is why early withdrawal is expensive.