What Is APY and How Does It Work?

When you compare savings accounts, you may see a percentage labeled APY. These three letters can help you understand how much interest your savings could earn over time.

APY stands for annual percentage yield. It measures the annual return on a deposit, including the effect of compound interest. This means it accounts for interest earned on your original deposit and, when interest compounds, on previously earned interest.

Understanding APY can help you compare traditional savings accounts, high-yield savings accounts, and certificates of deposit (CDs). It also helps you look beyond the advertised rate and understand the terms that affect your earnings.

What Does APY Stand For?

APY means annual percentage yield. Banks and credit unions use it to express how much interest a deposit account can earn over a year, taking compounding into account.

For example, an account might advertise a 4.00% APY. Under the assumptions used to calculate that yield, a $1,000 deposit would earn approximately $40 in interest over one year.

This example assumes the APY remains unchanged and that no additional deposits or withdrawals occur. It is an illustration, not a statement about currently available rates.

APY gives you a standardized way to understand the effect of interest and compounding. However, it does not account for every factor that may affect your financial results, such as fees, changing rates, or taxes.

How Does APY Work?

APY reflects the relationship between an account’s interest rate and its compounding frequency.

Compound interest occurs when interest becomes part of the balance used to calculate future interest. Over time, this can increase the amount earned compared with an arrangement that does not compound interest.

Consider a simplified example.

Suppose you deposit $1,000 into a savings account with a 4.00% annual interest rate, compounded annually.

• Initial deposit: $1,000
• Interest after the first year: $40
• Balance after the first year: $1,040

If the account continues to pay the same rate, the next year’s interest is calculated on $1,040 rather than just the original $1,000.

That means the second year’s interest would be $41.60, assuming annual compounding and no other account activity.

The extra $1.60 represents interest earned on the previous year’s interest.

Actual accounts may compound interest daily, monthly, or according to another schedule. APY reflects the effect of that compounding under the applicable calculation assumptions.

Does Compounding Frequency Matter?

Yes. When the stated annual interest rate is the same, more frequent compounding generally produces a higher effective annual yield.

For example, interest compounded daily is added to the balance more frequently than interest compounded annually. That can allow interest to begin earning additional interest sooner.

However, comparing compounding frequency alone is not enough. The advertised APY already accounts for compounding, making it a useful starting point when comparing deposit accounts.

APY vs. Interest Rate: What’s the Difference?

The interest rate tells you the stated rate paid on your deposit. APY shows the annual yield after accounting for compounding.

For example, two accounts may advertise the same interest rate but offer different APYs if their compounding arrangements differ.

Comparing APYs can make these differences easier to identify. Still, check account fees, balance requirements, and other conditions before comparing the overall value of each account.

How to Calculate APY

You can calculate APY using the following formula when an account has a nominal annual interest rate and compounds at regular intervals:

APY = (1 + r/n)^n − 1

In this formula:

• r is the annual interest rate expressed as a decimal.
• n is the number of compounding periods per year.

Multiply the result by 100 to express APY as a percentage.

A Hypothetical Calculation

Suppose a savings account pays a 4.00% annual interest rate and compounds monthly.

• Annual interest rate: 0.04
• Compounding periods: 12
• Initial deposit: $1,000

The calculation is:

APY = (1 + 0.04/12)^12 − 1 ≈ 0.040742, or 4.0742%.

The resulting APY is approximately 4.07%.

With a $1,000 balance, that corresponds to about $40.74 in interest over one year, assuming the rate stays constant and no other transactions occur.

This example illustrates why APY can be higher than the stated interest rate when interest compounds more than once a year. Actual account calculations may follow additional rules based on the account’s terms and applicable regulations.

Where Will You See APY?

APY appears in several types of deposit accounts. Understanding the differences can help you compare how each account handles interest and access to your money.

Traditional Savings Accounts

Traditional savings accounts let you keep money in a deposit account while earning interest. Their APYs vary by institution and account terms.

They may provide convenient access to savings, but you should check fees, minimum balances, and withdrawal conditions.

High-Yield Savings Accounts

High-yield savings accounts are designed to pay competitive interest compared with many traditional savings accounts.

Their APYs may be variable, meaning the bank can change the rate. A rate advertised when you open an account may not remain available indefinitely.

Learn more in our guide to What Is a High-Yield Savings Account?

Certificates of Deposit (CDs)

A CD generally requires you to leave a deposit in place for a specified term. In exchange, the institution offers interest under the CD’s terms.

Many CDs have a fixed rate for the term, but early withdrawals may trigger penalties. Check the maturity date and withdrawal rules before opening one.

Money Market Deposit Accounts

Money market deposit accounts are deposit products offered by banks and credit unions. They may pay interest and provide certain transaction features.

Do not confuse them with money market mutual funds, which are investment products and do not receive FDIC deposit insurance simply because their names sound similar.

What Should You Compare Besides APY?

A higher APY can mean more interest, but the advertised yield is only one part of an account’s terms.

Before choosing a savings product, consider these factors.

• Fees: Monthly maintenance fees can reduce the benefit of interest earned.
• Minimum balance: Some accounts require a minimum deposit or balance to qualify for an advertised APY.
• Rate changes: Variable APYs can rise or fall over time.
• Promotional offers: Introductory rates may apply only for a limited period or under specific conditions.
• Access to funds: CDs may restrict access before maturity or impose early withdrawal penalties.
• Deposit protection: Confirm whether the institution qualifies for FDIC or NCUA insurance and how applicable coverage limits and ownership categories work.

For eligible bank deposits, FDIC insurance protects depositors within applicable limits. Eligible credit union deposits may receive coverage through the NCUA’s share insurance system. Coverage depends on the institution, account ownership, and applicable rules.

You can review official information at FDIC.gov and NCUA.gov.

Is APY Guaranteed?

APY is not necessarily a promise that you will earn the same amount throughout the year.

For a variable-rate savings account, the institution may change the interest rate. If that happens, your actual earnings can differ from an estimate based on the opening APY.

A CD may offer a fixed rate for a specified term, subject to its contract. However, the conditions for earning the stated yield still matter, including whether you keep the deposit until maturity.

APY also does not mean your money is automatically insured. Deposit protection depends on the institution and account structure, not on the size of the advertised yield.

When reviewing an account, read its current disclosures to understand the rate, fees, and conditions that apply.

Bottom Line

APY, or annual percentage yield, helps you understand how much interest a deposit account can earn over a year, including the effect of compounding.

It is a useful starting point when comparing savings accounts and CDs. However, a higher APY does not tell you everything about an account.

Look at the interest rate, fees, minimum balance, access restrictions, and whether the yield can change. Checking these details gives you a clearer picture of how an account may fit your savings needs.