By Harpreet Singh | Last updated: September 20, 2026
Two savings accounts can advertise the same interest rate and still pay you different amounts. The difference is compounding, and the number that captures it is the annual percentage yield, or APY. This guide shows how APY is calculated, works through real examples, and explains what else to check before you open an account.
Key takeaways
- APY is the interest you earn over one year, including compounding, shown as a percentage.
- The formula is APY = (1 + r ÷ n)n − 1, where r is the stated rate and n is how many times interest compounds per year.
- The rate itself matters more than compounding frequency: on $10,000 at 4.00%, daily compounding earns only about $8 more per year than annual compounding.
- Look beyond the headline APY. Check fees, balance tiers, whether the rate is variable, and FDIC or NCUA insurance.
What is APY?
Annual percentage yield is the total interest a deposit earns in one year, expressed as a percentage of the balance, after accounting for compound interest. Compound interest means you earn interest on your original deposit and also on the interest already added to your balance.
In the United States, federal Truth in Savings rules require banks and credit unions to disclose APY on most consumer deposit accounts. Because institutions use the same calculation, APY lets you compare savings accounts, money market accounts and certificates of deposit (CDs) on equal terms.
How APY is calculated
The formula is:
APY = (1 + r ÷ n)n − 1
Here r is the stated annual interest rate as a decimal (4% is 0.04) and n is the number of compounding periods per year. This table shows $10,000 held for one year at a 4.00% stated rate, with no deposits or withdrawals:
| Compounding | Periods per year (n) | APY | Interest after one year |
|---|---|---|---|
| Annually | 1 | 4.00% | $400.00 |
| Quarterly | 4 | 4.06% | $406.04 |
| Monthly | 12 | 4.07% | $407.42 |
| Daily | 365 | 4.08% | $408.08 |
The gap between annual and daily compounding is about $8 on $10,000. A rate difference matters far more: an account paying 4.50% APY earns about $50 more per year on the same $10,000 than one paying 4.00% APY. That is why comparing APYs is worth the effort, but chasing tiny compounding differences is not.
APY vs. interest rate vs. APR
| Term | What it measures | Where you see it |
|---|---|---|
| Interest rate (stated rate) | The base rate before compounding is applied | Savings accounts, loans, credit cards |
| APY | What a deposit earns in a year, including compounding | Savings, money market accounts, CDs |
| APR | The yearly cost of borrowing | Loans, credit cards, mortgages |
When you save, a higher APY is better. When you borrow, a lower APR is better. Keep in mind that a credit card APR does not include the effect of compounding, so the real cost of carrying a balance can be higher than the APR suggests.
How a balance grows: a worked example
Assume a hypothetical 4.00% APY that stays the same and you make no deposits. Then $10,000 grows to about $12,167 after 5 years ($10,000 × 1.045) and about $14,802 after 10 years ($10,000 × 1.0410). Savings rates change over time, so treat these numbers as an illustration of compounding, not a forecast.
Fixed vs. variable APY
Most savings and money market accounts have variable rates. The bank can raise or lower your APY at any time, often following changes in the Federal Reserve’s interest rate policy. A CD usually locks in a fixed APY for its term, but withdrawing early typically triggers a penalty. If you expect rates to fall, a CD can lock in today’s yield. If you may need the money, a savings account gives you flexibility.
What to check besides APY
- Fees: monthly maintenance fees can cancel out a higher APY.
- Balance tiers: some accounts pay the advertised APY only on balances above a certain amount.
- Promotional rates: a high introductory APY may drop after a few months.
- Withdrawal and transfer rules: check limits, transfer times and any penalties.
- Deposit insurance: the FDIC insures deposits at member banks, and the NCUA insures deposits at federally insured credit unions, up to $250,000 per depositor, per insured institution, per ownership category.
Taxes on savings interest
Interest you earn is generally taxable income at the federal level. Banks typically send Form 1099-INT when you earn $10 or more in interest during the year, but you are expected to report all interest income, even if you do not receive a form. Rules vary by state, so check with the IRS or a tax professional for your situation.
Does inflation affect your savings?
Yes. Inflation reduces what your money can buy. As a simple approximation, your real return is your APY minus the inflation rate. In a hypothetical year with a 4.00% APY and 3.00% inflation, your purchasing power grows by roughly 1%. If inflation is higher than your APY, your savings lose buying power even though the balance is growing.
How to compare savings accounts in 5 steps
- List the APYs of the accounts you are considering and note whether each is fixed or variable.
- Read the fee schedule and minimum balance requirements.
- Confirm FDIC or NCUA insurance and stay within the $250,000 limit at each institution.
- Check how long transfers take and whether there are withdrawal limits.
- Choose the account with the best combination of APY, low fees and access, then recheck the rate every few months.
Frequently asked questions
Is a higher APY always better?
Usually, but not always. A higher APY can come with fees, balance requirements or a rate that drops after a promotional period. Compare the full terms.
Can my APY change?
Yes, on variable-rate accounts. The bank can change the APY at any time, usually with notice. CDs generally keep a fixed APY until they mature.
Is APY the same as interest rate?
No. The interest rate is the base rate. APY includes the effect of compounding, so it is equal to or slightly higher than the stated rate.
Sources and further reading
- FDIC: Deposit insurance
- CFPB: Regulation DD (Truth in Savings)
- NCUA: Share insurance for credit union members
- IRS: About Form 1099-INT
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About the author: Harpreet Singh is a content publisher and SEO specialist who researches and explains U.S. personal finance topics for Finance Glide. He is not a licensed financial advisor. This article is educational and is not personal financial advice. See our Disclaimer and About page, or contact us to report an error.
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