The amount you earn depends on your balance, the APY your bank offers, and how long the money sits there
Interest on a savings account is calculated by multiplying your balance by the annual percentage yield (APY) and dividing by the number of days in a year. If you have $10,000 in an account with a 4.5% APY, you earn roughly $450 per year — but that breaks down to about $1.23 per day, and most banks add that interest monthly or daily depending on their terms.
The real number that matters is what your specific bank pays right now. APY rates change constantly and vary widely between institutions. A traditional bank might offer 0.01% APY on a savings account, while an online bank might offer 4.5% or higher on the same balance. Over a year, that difference turns $10,000 into either $10,001 or $10,450.
Interest compounds, meaning you earn interest on the interest you've already earned — but only if the bank compounds daily or monthly rather than annually. Most modern savings accounts compound daily, so your balance grows slightly faster than a straightforward calculation would suggest.
Key Takeaways
- Your earnings equal your balance multiplied by the APY, divided by 365 days, then multiplied by the number of days your money stays in the account.
- APY rates vary from under 0.01% at traditional banks to 4.5% or higher at online banks, making the choice of bank far more important than the size of your balance.
- Daily compounding means you earn small amounts of interest every day, and that interest itself earns interest, though the effect is modest on most balances.
- Your bank must disclose the APY in writing before you open the account, and that rate can change at any time after you deposit money.
How the calculation actually works
The formula banks use is: Interest = (Balance × APY) ÷ 365 × Number of Days. If you deposit $5,000 in an account with 4.0% APY and leave it untouched for 90 days, you earn roughly $49.32. After 365 days, you earn $200.
Banks that compound daily recalculate this every single day, using your current balance. So if you deposit $5,000 on January 1st and add $1,000 on February 1st, the second deposit earns interest for only 334 days that year, not 365. This is why the exact timing of deposits and withdrawals matters slightly.
Most banks show you the projected annual interest in their account disclosures, listed as APY. Some still list APR (annual percentage rate) instead, which does not account for compounding and will understate what you actually earn. Always look for APY, not APR, when comparing accounts.
Why the bank you choose matters far more than your balance
The difference between a 0.01% APY and a 4.5% APY is roughly $450 per year on a $10,000 balance. That is not a small rounding error — it is the difference between earning almost nothing and earning enough to cover a month of groceries. Yet many people keep savings at the bank where they have their checking account, often without knowing what rate they are earning.
Online banks and credit unions typically offer higher rates because they have lower overhead costs than brick-and-mortar branches. They pass some of that savings to depositors. Traditional banks often offer rates under 0.1% because they rely on checking account customers and do not compete aggressively for savings balances.
The trade-off is access. An online bank has no physical branch, so you cannot walk in and withdraw cash. Most online banks are FDIC-insured, meaning your money is protected up to $250,000 even if the bank fails, but you should verify this before opening an account. Credit unions offer similar protections through the NCUA.
What happens when rates change
Banks can lower your APY at any time after you open the account, and they usually notify you by email or mail a few days before the change takes effect. You have no contractual right to keep the old rate. When the Federal Reserve raises or lowers its benchmark rate, savings account APYs typically follow within weeks, though the timing varies by bank.
Rate cuts happen faster than rate increases. When the Fed raises rates, competitive banks raise their savings rates quickly to attract deposits. When the Fed cuts rates, banks lower savings rates more slowly because they want to keep the deposits they have. This asymmetry means you should move money to a higher-paying account when rates rise, but you do not need to panic when they fall.
Some banks offer promotional rates that are higher than their standard rate for a limited time — usually 3 to 12 months. After the promotional period ends, your rate drops to the standard rate. Read the fine print to see when the promotion ends and what the regular rate will be.
How much you actually earn on common balances
| Balance | At 0.01% APY | At 1.0% APY | At 4.5% APY |
|---|---|---|---|
| $1,000 | $0.10 per year | $10 per year | $45 per year |
| $10,000 | $1 per year | $100 per year | $450 per year |
| $50,000 | $5 per year | $500 per year | $2,250 per year |
| $100,000 | $10 per year | $1,000 per year | $4,500 per year |
These figures assume the money stays in the account for the full year with no deposits or withdrawals. If you add money partway through the year, that new deposit earns interest only for the remaining days. If you withdraw money, you lose interest on that amount going forward.
The difference between a 1% account and a 4.5% account on a $50,000 balance is $1,750 per year. That is real money — enough to cover a car payment or several months of utilities. Yet many people do not check their savings rate because they assume all banks pay roughly the same. They do not.
When interest gets paid to your account
Banks add interest to your account on different schedules. Some add it daily, some monthly, and a few still add it quarterly or annually. Daily compounding is best because you earn interest on the interest sooner, though the difference is small on most balances.
You can see when interest was added by checking your account statement or transaction history. Look for a deposit labeled "interest paid" or similar. If you do not see any interest deposits over several months, your APY is likely very low or you have a checking account, not a savings account.
Interest is taxable income. Your bank will send you a 1099-INT form at the end of the year if you earned $10 or more in interest. You report this on your tax return. This is one reason why earning interest on a savings account is better than keeping cash in a non-interest-bearing account — at least you get something for the tax burden.
How to find out what you are earning right now
Log into your bank's website or app and look for your account details or account summary. The APY should be listed there, along with the current balance and any recent interest payments. If you cannot find it online, call your bank's customer service line and ask for the current APY on your savings account.
Write down the APY and the date you checked it. Then use the formula above to calculate what you should earn over the next year. If the number seems low compared to what other banks are offering, you have a decision to make: stay for convenience, or move the money to earn more.
Moving money between banks is straightforward. Most banks can transfer funds electronically within one to three business days. You do not lose FDIC protection during the transfer, and you do not owe any penalty for moving money out of a savings account (unlike certificates of deposit, which charge early withdrawal fees).
Frequently Asked Questions
Does my savings account earn interest if I do not touch the money?
Yes. As long as the account is open and has a balance, interest accrues every day, even if you never make another deposit or withdrawal. The bank adds the interest to your account on its regular schedule — usually monthly or daily — so your balance grows automatically.
What if I withdraw money partway through the month?
You lose interest on the amount you withdrew for the days after the withdrawal. If you withdraw $5,000 on the 15th of a month, you earn interest on that $5,000 only for the first 14 or 15 days, depending on how your bank counts. The remaining balance continues to earn interest normally.
Is the interest I earn taxable?
Yes. Any interest your savings account earns is taxable income. If you earn $10 or more in a calendar year, your bank sends you a 1099-INT form, and you report it on your tax return. This applies even if you did not withdraw the money.
Can a bank lower my interest rate without warning?
Yes. Banks can change your APY at any time after you open the account. They usually notify you a few days before the change takes effect, but you have no right to keep the old rate. If your rate drops significantly, you can move your money to a different bank.
Why do online banks pay more interest than traditional banks?
Online banks have lower operating costs because they do not maintain physical branches. They pass some of those savings to depositors by offering higher APY rates. Traditional banks rely on checking account customers and do not compete as aggressively for savings balances, so their rates stay lower.