What determines how much interest your savings account earns
The amount of interest you earn depends on three things: the annual percentage yield (APY) the bank offers, how much money you have in the account, and how long it stays there. A bank offering 4.5% APY on $10,000 will pay you roughly $450 per year, but only if the money sits untouched for the full twelve months. If you withdraw half the balance after six months, you earn interest only on the average balance held.
Banks set their own APY rates based on what the Federal Reserve charges them to borrow money. When the Fed raises its benchmark rate, banks typically raise savings APY within weeks. When the Fed cuts rates, banks lower savings APY much more slowly—sometimes not at all. This is why the same bank might offer 0.01% one year and 4.75% the next, and why shopping around matters.
The type of account also changes the rate. A regular savings account usually earns less than a money market account or a certificate of deposit (CD) with the same bank. Online banks almost always pay more than brick-and-mortar banks because they have lower overhead costs.
Key Takeaways
- Interest earned equals the APY rate multiplied by your average account balance, divided by 12 for each month the money stays deposited.
- Banks change their APY rates frequently, and online banks typically pay 3 to 5 times more than traditional banks on the same account type.
- Money market accounts and CDs pay higher rates than regular savings accounts, but CDs lock your money away for a set term.
- Interest compounds daily or monthly depending on the bank, meaning you earn interest on interest, but the difference is small on most balances.
How to calculate interest on your specific balance
The formula is straightforward: multiply your balance by the APY, then divide by 365 (or 360, depending on the bank's method). If you have $5,000 in an account earning 4.0% APY, you earn roughly $200 per year, or about $16.67 per month. If the balance changes during the month, the bank calculates interest on the average balance for that period.
Most banks compound interest daily, meaning they calculate how much you've earned and add it back to your account each day. That interest then earns interest itself the next day. On a $10,000 balance at 4.5% APY with daily compounding, you earn about $4.59 in the first month. The second month you earn slightly more because your balance is now $10,004.59. Over a year, daily compounding adds roughly $23 more than simple annual interest would—not huge, but real.
You can find the exact interest formula on your bank's website or in the account disclosure document they send you. Some banks use a 365-day year, others use 360. Some compound daily, others monthly. These small differences matter most on large balances held for years.
Why APY varies so much between banks
Online banks pay significantly more than traditional banks because they don't maintain physical branches, employ as many staff, or spend money on advertising. A brick-and-mortar bank might offer 0.05% APY on savings while an online bank offers 4.5% APY on the exact same account type. That difference costs you thousands of dollars per year on a six-figure balance.
Banks also offer promotional rates to new customers. A bank might advertise 5.0% APY for the first three months, then drop to 3.5% after that. Read the fine print to see when the rate changes and what the long-term rate will be. Some promotional rates require a minimum deposit or monthly transfers to may have access to.
Credit unions sometimes pay higher rates than banks, especially on savings accounts and CDs. You must be a member to open an account, but membership is often free or costs $5 to $25 one time. If you work in a specific industry or live in a certain area, you may already be may be able to access for a credit union.
The difference between APY and interest rate
Banks quote two numbers: the interest rate and the APY. The interest rate is the base percentage the bank pays. The APY includes the effect of compounding—how many times per year the bank adds interest back to your account. On most savings accounts, the difference is tiny because compounding happens frequently. On a $1,000 balance at 4.0%, the difference between a 4.0% interest rate and 4.0% APY is less than $1 per year.
Always compare banks using APY, not the interest rate. APY is the number that tells you what you'll actually earn. If one bank advertises a 4.0% interest rate and another advertises 4.0% APY, the second bank will pay you more because its rate compounds more often.
How interest payments reach your account
Banks deposit interest into your savings account automatically on a schedule they set—usually monthly or quarterly. You don't have to do anything to receive it. The interest appears as a deposit in your transaction history, and your balance grows. Some banks show interest as a separate line item; others roll it into your balance without labeling it.
If you close the account before the interest is deposited, you forfeit the interest earned up to that point. If you close on the 15th of a month and the bank deposits interest on the last day of the month, you lose that month's interest. Check your bank's policy before closing an account.
Interest is taxable income. Banks 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. The IRS taxes interest at your ordinary income tax rate, not at a special rate.
When higher APY accounts make sense and when they don't
A high-yield savings account makes sense if you have money you won't need for several months or longer. If you're saving for a down payment in six months, moving $50,000 from a 0.05% account to a 4.5% account earns you roughly $1,125 extra. That's worth the five minutes it takes to open the new account and transfer the money.
High-yield savings accounts make less sense for money you access frequently. Some online banks limit withdrawals or charge fees if you exceed a certain number per month. If you're dipping into the account weekly, a local bank with no withdrawal limits might be more practical, even if the rate is lower.
CDs pay higher rates than savings accounts but lock your money away. If you need the money before the CD matures, you pay an early withdrawal penalty that can wipe out all the interest you've earned. CDs make sense only for money you're certain you won't need for the full term.
Frequently Asked Questions
How often do banks change their savings APY?
Banks can change APY at any time without notice, though most change within days or weeks of a Federal Reserve rate change. Check your bank's website monthly or set a calendar reminder to compare rates. If your bank drops its rate significantly, moving to a higher-paying bank takes about a week and costs nothing.
Do I pay taxes on savings account interest?
Yes. Interest is taxable income at your ordinary tax rate. If you earn $100 in interest, you report it as income on your tax return. Banks send a 1099-INT form if you earn $10 or more. Even if you don't receive a form, you still owe tax on the interest.
What's the difference between a savings account and a money market account?
Money market accounts usually pay higher APY than savings accounts but may require a larger minimum balance and limit your withdrawals. Both are FDIC-insured up to $250,000. If you want the highest rate and don't need frequent access, a money market account may pay more. If you want flexibility, a savings account is simpler.
Can I move my money to a higher-paying bank without losing interest?
Yes. Interest accrues up to the day you withdraw. Once you move the money to a new bank, you start earning the new bank's rate immediately. There's no penalty for switching banks, and the transfer typically takes three to five business days. You don't lose any interest during the transfer.
Why does my bank pay almost no interest?
Traditional banks often pay 0.01% to 0.05% because they don't compete on rate—they rely on branch convenience and customer inertia. Online banks and credit unions compete primarily on rate because they have no branches to visit. If your bank pays nearly nothing, moving your money to an online bank or credit union earning 4% or more is usually worth doing.