What is APY and how is it different from an interest rate
APY includes compounding, so it shows what you really earn in a year. Interest rate alone doesn't.
The quick difference: an interest rate is the basic percentage a bank pays on your deposit, while APY (annual percentage yield) also includes the effect of compounding, so it tells you what you actually earn over a full year. For example, a savings account with a 4.00% interest rate that compounds monthly might have an APY of about 4.07%. That means a $10,000 deposit would earn roughly $407 in a year, not $400.
What is an interest rate?
An interest rate on a savings account is the simple percentage of your balance that the bank pays you, usually quoted per year. If you put $1,000 in an account with a 4% interest rate and no compounding, you would earn $40 after one year. That is simple interest: it only applies to your original deposit, not to any interest you have already earned.
Interest rates also appear on loans. When you borrow money, the interest rate is the cost of borrowing, expressed as a percentage of the loan amount. For instance, the average credit card APR (which is similar to an interest rate but includes some fees) is around 21%–23%, according to the Federal Reserve. That is a very different context from savings, but the basic idea is the same: a percentage of the balance.
For savings, banks often advertise the interest rate, but they are required to also show the APY. The APY is the more accurate number because it accounts for compounding.
What is APY?
APY stands for annual percentage yield. It is the real rate of return you earn on a deposit over one year, assuming you leave the money in the account and do not add or withdraw. The key difference from the interest rate is that APY includes compound interest.
Compound interest means you earn interest on your interest. Many savings accounts compound daily or monthly. So after the first month, you earn interest on the original deposit plus the interest from the previous month. Over a year, that extra growth makes the APY higher than the stated interest rate.
For example, a high-yield savings account might advertise an APY of 4.00%. The underlying interest rate might be 3.92%, but because interest is compounded daily, you end up with 4.00% growth over the year. The APY is the number you should compare when shopping for a savings account, because it gives you an apples-to-apples view of what you will earn.
How APY and interest rate differ: side-by-side
| Feature | Interest Rate | APY |
|---|---|---|
| Includes compounding | No | Yes |
| Shows true annual earnings | No (understates) | Yes |
| Used for savings accounts | Sometimes advertised | Usually advertised |
| Used for loans | Yes (cost of borrowing) | No (not typical) |
| Example: $1,000 at 4% for one year | $40 | $40.74 (if compounded monthly) |
As the table shows, the interest rate is the base percentage, while APY is the actual percentage you earn after compounding. For a one-year CD with a 4% interest rate compounded monthly, the APY is about 4.07%, so a $1,000 deposit earns $40.74, not $40.
Worked example: Maya's savings account
Let's walk through a realistic example. Maya opens a high-yield savings account with $5,000. The bank advertises an interest rate of 3.75% and an APY of 3.82%, with interest compounded monthly. She does not make any deposits or withdrawals for one year.
To find the monthly interest rate, divide the annual rate by 12: 3.75% / 12 = 0.3125% per month. In decimal form, that is 0.003125.
Month 1: Maya earns $5,000 × 0.003125 = $15.63. Her balance becomes $5,015.63.
Month 2: She earns interest on the new balance: $5,015.63 × 0.003125 = $15.67. Her balance becomes $5,031.30.
If you repeat that for 12 months, the ending balance is about $5,191. That means she earned $191 in interest. The APY of 3.82% gives the same result: $5,000 × 0.0382 = $191. The simple interest rate alone (3.75%) would suggest only $187.50. The difference is about $3.50, which is the compounding effect.
Here is a table of the first few months:
| Month | Starting Balance | Interest Earned | Ending Balance |
|---|---|---|---|
| 1 | $5,000.00 | $15.63 | $5,015.63 |
| 2 | $5,015.63 | $15.67 | $5,031.30 |
| 3 | $5,031.30 | $15.72 | $5,047.02 |
| 12 | $5,175.83 | $16.17 | $5,191.00 |
This example shows why APY is the number to look at when comparing savings accounts. Two accounts might have the same interest rate but different compounding frequencies, leading to different APYs and different earnings.
What people get wrong about APY and interest rate
Mistake 1: Confusing the interest rate with the APY. People often compare the interest rate when shopping for a savings account, but the APY is the true annual return. If you compare interest rates only, you might pick an account that actually earns less because it compounds less frequently.
Mistake 2: Thinking APY is the same as the interest rate on a loan. APY is used for deposits, not loans. For loans, you look at the APR (annual percentage rate), which includes interest and certain fees. Mixing these up can lead to confusion about what you owe or earn.
Mistake 3: Assuming APY is fixed. Most savings accounts have a variable APY, meaning the bank can change it at any time, often in response to the federal funds rate. The Federal Reserve sets a target range for that rate, which influences what banks pay on savings. A high APY today might not be the same next year.
Mistake 4: Ignoring the effect of withdrawals. APY assumes you leave your money untouched for a year. If you withdraw money, you earn less because the balance is lower for part of the year. The APY is a projection, not a guarantee.
How to tell which number you are looking at
When you see an advertisement for a savings account, it will usually say something like "4.00% APY." That is the number you want to compare. If you see just an interest rate, ask for the APY or look for it in the account details. Banks are required to disclose the APY for deposit accounts under federal truth-in-savings rules.
For loans, the situation is different. You will see an interest rate and an APR. The APR includes the interest rate plus certain fees, so it is a more complete measure of the cost of borrowing. For example, a mortgage might have an interest rate of 6.50% but an APR of 6.60% because of closing costs. The average 30-year fixed mortgage rate is currently around 6.25%–7.00%, according to the St. Louis Fed. That is the interest rate, not the APR.
If you are comparing savings accounts, always use APY. If you are comparing loans, use APR. Remember: APY is for what you earn, APR is for what you pay.
Putting it together
APY and interest rate are related but not the same. The interest rate is the base percentage, while APY includes compounding and shows your true annual earnings. When you look at a savings account, the APY is the number that matters most because it tells you what you will actually earn over a year.
For more on how savings accounts work, see our guide on how a high-yield savings account works. If you want to calculate potential earnings for different scenarios, try our compound interest calculator.
Key takeaways
- APY includes compound interest, so it is always higher than the interest rate for the same account.
- When comparing savings accounts, look at APY, not just the interest rate.
- APY assumes you leave your money in the account for a full year without withdrawals.
- For loans, use APR (which includes fees) rather than APY.
What This Means For Your Money
How this could affect the money decisions in front of you.
What to understand
APY is the true annual return on savings because it includes compounding, so it is the right number to compare.
What to watch for
APYs on savings accounts are variable and can change with the federal funds rate, so a high rate today may not last.
Put it to work
Frequently asked questions
Why is APY higher than the interest rate?
Does a higher APY always mean more earnings?
What is the difference between APY and APR?
How often do banks compound interest?
Sources
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Written by Mohammed Salman — Editorial Team
The MoneyPilot editorial team researches and writes every guide on the site. We explain how consumer finance works in plain English, starting from primary sources (the CFPB, the Federal Reserve, the FDIC and NCUA, the SEC and IRS) and we label every estimate and example as illustrative. Guides with formulas or regulatory detail are also checked by a financial reviewer before they are marked as reviewed. See our editorial policy for how a guide is researched, fact-checked, and kept current.
More from Mohammed Salman →This article is educational information only. It is not financial, investment, or tax advice. Investing and cryptocurrency involve risk, including the possible loss of principal. Verify details with a qualified professional. It was drafted with AI assistance and reviewed by the MoneyPilot editorial team before publication; see our Editorial Policy.
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