The amount you earn depends on your balance, the APY, and how long the money sits there

Interest earned in a savings account is calculated by multiplying your balance by the annual percentage yield (APY), then dividing by the number of days in a year. If you keep $10,000 in an account with a 4.5% APY for a full year, you earn $450. If you keep it for six months, you earn roughly $225. The catch: most banks compound interest daily or monthly, which means you earn a tiny amount of interest on the interest itself—but the difference is usually small enough that you can calculate it roughly by hand.

The real variables are the APY itself and how long your money stays in the account. A high-yield savings account at an online bank might offer 4% to 5% APY right now. A traditional brick-and-mortar bank might offer 0.01% to 0.5%. That difference compounds fast. On $10,000 over one year, the gap between 0.01% and 4.5% is $449—nearly $450 in lost earnings.

Your balance also matters. If you deposit $1,000 one month and withdraw it the next, you don't earn a full year's worth of interest. Banks typically calculate interest based on your daily balance or your average balance over the statement period. Some accounts require a minimum balance to earn any interest at all, or they pay a higher rate only on balances above a certain threshold.

Key Takeaways

  • Interest earned equals your balance multiplied by the APY, divided by 365 days—so $10,000 at 4.5% APY earns roughly $450 per year.
  • Online banks and credit unions typically offer 4% to 5% APY on savings accounts, while traditional banks often offer less than 1%.
  • Interest compounds daily or monthly at most banks, meaning you earn interest on your interest, though the effect is small on typical balances.
  • The longer your money stays in the account and the higher your balance, the more interest you accumulate.
  • Some accounts require a minimum balance to earn any interest, and some pay higher rates only on amounts above a certain threshold.

How compounding changes the math

When a bank compounds interest daily, it calculates how much you've earned each day and adds that to your balance. The next day, you earn interest on the new, slightly larger balance. Over a year, this compounds into a real difference—though not a huge one on most savings account balances.

The difference between simple interest and compound interest is clearest on larger balances held for longer periods. On $50,000 at 4.5% APY compounded daily, you earn about $2,296 over a year, not $2,250. That extra $46 comes from compounding. On $1,000, the difference is less than a dollar. Most banks disclose their compounding method in the account terms, usually buried in the fine print or on a rates page.

Some savings accounts compound monthly instead of daily. Monthly compounding earns you slightly less than daily compounding, but the difference is small—usually a few dollars per year on a typical balance. If you're comparing two accounts and one compounds daily while the other compounds monthly, the daily compounding account is marginally better, but the APY itself matters far more.

Why APY varies so much between banks

The APY a bank offers on savings accounts is tied to the federal funds rate, which the Federal Reserve sets. When the Fed raises rates, banks raise the APY they offer on savings accounts. When the Fed cuts rates, banks cut APY. But banks don't all move at the same speed or to the same degree.

Online banks typically offer higher APY than traditional banks because they have lower overhead costs—no branches, fewer employees, cheaper real estate. They pass some of that savings to customers in the form of higher rates. A traditional bank might offer 0.5% APY while an online bank offers 4.5% APY on the exact same type of account. Both are real, and both are legal. The online bank is simply choosing to compete on rate.

Credit unions often offer competitive rates too, sometimes matching or beating online banks. Credit unions are member-owned nonprofits, so they can return earnings to members through higher rates. If you're a member of a credit union, check their savings rate before assuming an online bank is your best option.

What happens to your interest if you withdraw money early

Most savings accounts have no penalty for withdrawals, so you can take your money out whenever you want and keep all the interest you've earned up to that point. If you deposit $5,000 on January 1 and withdraw it on June 30, you keep the interest earned for those six months. The bank doesn't claw it back.

Money market accounts and some high-yield savings accounts may limit how many withdrawals you can make per month without a fee. Federal rules once capped withdrawals at six per month, but that rule was suspended. Individual banks still enforce their own limits, usually allowing three to six free withdrawals per statement period. After that, you might pay $10 to $25 per withdrawal. Check your account terms to see if limits apply.

Certificates of deposit (CDs) are different. If you withdraw money from a CD before the maturity date, you pay an early withdrawal penalty that can eat into or eliminate your interest earnings. A CD is a commitment to leave the money untouched for a set period—usually three months to five years—in exchange for a may provide, often higher APY.

How to compare interest earnings across accounts

The APY is the only number you need to compare. It already includes the effect of compounding, so you don't have to do any math beyond multiplying your balance by the APY to estimate your annual earnings. If Account A offers 4.5% APY and Account B offers 3.8% APY, Account A will earn you more interest on the same balance, period.

When comparing accounts, also check whether there are monthly fees that reduce your earnings. Some banks charge a monthly maintenance fee of $5 to $15. On a $1,000 balance earning 4.5% APY, a $5 monthly fee ($60 per year) cuts your net earnings nearly in half. Many banks waive the fee if you maintain a minimum balance or set up direct deposit, so read the fine print.

Use an online calculator if you want to see exact earnings over a specific time period. Enter your balance, the APY, and the number of months or years, and the calculator shows you the total interest earned. This is useful when you're deciding between two accounts or trying to estimate how much you'll earn by a specific date.

Interest rates change—here's what that means for you

The APY on a savings account is not locked in. Banks can raise or lower it at any time, and they usually do when the Federal Reserve changes the federal funds rate. If the Fed raises rates, you might see your APY increase within days or weeks. If the Fed cuts rates, your APY will likely drop.

This is why the APY you see today might not be the APY you earn six months from now. If you open an account at 4.5% APY and the Fed cuts rates, your bank might lower the APY to 3.8% or lower. You don't lose the interest you've already earned, but your future earnings will be smaller. This is one reason to move money to a higher-rate account if your current bank drops its rate significantly.

Some banks are slower to raise rates when the Fed increases them, but faster to cut rates when the Fed decreases them. If you're in an account with a bank that's slow to raise rates, switching to a competitor with a higher current APY can make sense. The difference between 3.5% and 4.5% APY on $25,000 is $250 per year—real money worth a 10-minute account transfer.

Frequently Asked Questions

How often is interest added to my savings account?

Most banks compound and credit interest daily or monthly. Daily compounding is slightly better, but the difference is small. You'll see the interest posted to your account balance on your statement, usually once per month. Some banks show daily interest accrual in your online account, even if it's credited monthly.

Do I have to pay taxes on savings account interest?

Yes. Interest earned on a savings account is taxable income. Banks send you a 1099-INT form if you earn $10 or more in interest during the year. You report this on your tax return. The tax rate depends on your overall income and tax bracket, not on the interest rate itself.

What's the difference between APY and APR on a savings account?

APY (annual percentage yield) includes the effect of compounding, while APR (annual percentage rate) does not. For savings accounts, always look at the APY—it's the real number that tells you how much you'll earn. APR is used for loans and credit cards, not savings.

Can I earn interest on money I just deposited?

Yes, but the timing depends on when the bank posts the deposit. If you deposit money on a Friday and the bank doesn't post it until Monday, interest accrual usually starts Monday. Some banks begin accruing interest the same day for deposits made before a certain time. Check your bank's deposit posting policy.

Is there a maximum amount of interest I can earn?

No. There's no limit on how much interest you can earn in a savings account. However, the Federal Deposit Insurance Corporation (FDIC) insures only up to $250,000 per depositor per bank. If you have more than $250,000, the excess is not insured against bank failure, though you still earn interest on it.