What determines your savings account interest

The amount of interest you earn depends on three things: the annual percentage yield (APY) the bank offers, how much money you keep in the account, and how long it stays there. A bank sets its APY based on what the Federal Reserve charges banks to borrow money—when that rate goes up, banks raise savings rates; when it goes down, they lower them. Your bank may also pay different rates depending on the account type: money market accounts often pay more than basic savings accounts, and high-yield savings accounts pay significantly more than either.

The actual dollars you earn follow a simple formula: multiply your balance by the APY, then divide by 365 (or 360, depending on the bank). If you have $10,000 in an account paying 4.5% APY, you earn roughly $450 per year, or about $37.50 per month. But that assumes your balance stays constant. Most banks compound interest daily or monthly, meaning they calculate interest on your interest, so the longer money sits there, the more you earn.

Interest rates change frequently. Banks adjust their rates whenever the Federal Reserve moves, and they can change them downward without notice. If you opened a savings account at 5.0% APY six months ago, your rate may now be 4.2%. Check your account statements or log into your bank's website to see what you're actually earning right now.

Key Takeaways

  • Your interest earnings equal your account balance multiplied by the APY your bank offers, divided by 365 days.
  • Banks set their rates based on Federal Reserve policy, so rates rise when the Fed raises its benchmark rate and fall when it lowers it.
  • High-yield savings accounts typically pay 4% to 5% APY, while traditional bank savings accounts often pay 0.01% to 0.5%.
  • Interest compounds daily or monthly at most banks, meaning you earn interest on the interest you've already accumulated.
  • Your bank can lower your rate at any time, so the APY you see today may not be what you earn next month.

How compound interest grows your money over time

Compound interest means the bank pays interest on your principal balance plus all the interest you've already earned. If you deposit $5,000 at 4.5% APY and never touch it, after one year you'll have $5,225.63 (not exactly $5,225, because the bank compounds daily). After five years, you'll have $6,272.48. After ten years, $7,744.25. The longer your money sits, the more the compounding effect adds up.

The difference between simple and compound interest becomes obvious over longer periods. With simple interest, $5,000 at 4.5% would earn $225 per year, every year—$2,250 over ten years. With daily compounding, you earn $2,744.25 over the same period. That extra $494 comes entirely from earning interest on your interest.

Your bank's compounding frequency matters slightly. Daily compounding (the most common) earns you a bit more than monthly compounding, which earns more than quarterly. The difference is usually a few dollars per year on a typical balance, but it adds up if you're keeping a large amount in savings.

Why rates differ between banks and account types

Banks compete for deposits by offering different rates. A large national bank like Chase or Bank of America typically pays 0.01% to 0.5% APY on savings accounts because they have physical branches, ATM networks, and customer service staff—those costs come out of their profits. An online-only bank like Marcus or Ally has no branches and lower overhead, so they can pay 4% to 5% APY and still make money.

Within the same bank, different account types earn different rates. A basic savings account might pay 0.05% APY, while a money market account at the same bank pays 1.5% APY. High-yield savings accounts, which are offered mostly by online banks, consistently pay the highest rates—currently in the 4% to 5% range, though this changes as Federal Reserve policy shifts.

Credit unions sometimes offer competitive rates too, though they vary widely. Some credit unions pay 4% or higher on savings, while others pay less than 1%. Call your credit union or check their website to see what they're currently offering.

How to calculate interest on your specific balance

To estimate what you'll earn, use this formula: (Balance × APY) ÷ 365 = Annual Interest. If you have $25,000 in an account paying 4.5% APY, you earn roughly $1,012.50 per year, or about $84 per month. Most banks show your earned interest on your monthly statement, so you can also just check there to see what you actually received.

If your balance changes during the month—you deposit $5,000 or withdraw $2,000—the bank recalculates based on your daily balance. Some banks use the average daily balance method, which adds up your balance each day and divides by the number of days in the month. Others use the daily balance method, which compounds interest each day on whatever you had that day. The difference is small but real: daily balance compounding pays slightly more.

Online calculators can show you projections. Enter your starting balance, APY, and how many years you plan to keep the money, and the calculator shows you the total with compounding. These are estimates—your actual earnings will differ if rates change or you add or withdraw money—but they give you a realistic picture of what to expect.

What happens when the Federal Reserve changes rates

When the Federal Reserve raises its benchmark interest rate, banks usually raise savings rates within days or weeks. When the Fed cuts rates, banks lower savings rates more slowly—sometimes taking months. This lag means you might keep earning a higher rate for a while after the Fed cuts, but you'll also see your rate drop faster than you'd like when the Fed raises.

The Fed's rate changes affect all banks, but not equally. Online banks typically raise rates faster than traditional banks because they're competing aggressively for deposits. A large national bank might raise its savings rate by 0.25% after a Fed increase, while an online bank raises by 0.5% or more. When the Fed cuts, online banks often cut faster too, so don't assume your rate will stay high forever.

You can track the Fed's rate decisions on the Federal Reserve's website. The Fed meets eight times per year and announces whether it's raising, lowering, or holding rates steady. After each announcement, check your bank's website to see if they've changed your rate.

Comparing savings accounts across different banks

The APY is the only number that matters when comparing savings accounts—ignore the interest rate, which is slightly lower and less useful for comparison. Look at the APY each bank is currently offering, not what they offered last year. Rates change constantly, so a bank that paid 5% three months ago might pay 4.2% today.

Check whether the bank compounds daily or monthly (daily is better), whether there are fees that reduce your earnings, and whether there's a minimum balance requirement. Some banks pay lower rates if your balance drops below $10,000 or $25,000. A few banks charge monthly maintenance fees that eat into your interest earnings.

Use a rate comparison site like Bankrate or DepositAccounts to see current rates across multiple banks. These sites update daily and show you which banks are paying the most. You can also visit each bank's website directly—the APY is usually displayed prominently on the savings account page.

Frequently Asked Questions

Is the interest I earn on a savings account taxed?

Yes. Interest income is taxable as ordinary income on your federal tax return. Banks send you a 1099-INT form if you earned $10 or more in interest during the year. You report this on your tax return, and you'll owe federal income tax on it (and state income tax in most states). This is why a high-yield savings account earning $500 per year means you'll owe roughly $100 to $150 in taxes, depending on your tax bracket.

Can a bank lower my interest rate without telling me?

Yes. Banks can lower savings rates at any time without advance notice. They're required to notify you of the change, but often that notification comes in a mailed statement or an email you might miss. Check your account online or call your bank if you haven't seen a rate change in several months—you may be earning less than you think.

Why do some savings accounts pay almost nothing?

Traditional banks with physical locations have higher costs and less pressure to compete on rates, so they pay 0.01% to 0.5% APY. Online banks have lower overhead and compete aggressively, so they pay 4% to 5%. If your bank is paying less than 1%, you're likely losing money to inflation—your balance grows, but it buys less each year.

Does moving money between savings accounts affect my interest?

No. Interest is calculated on your daily balance, so moving $5,000 from one savings account to another doesn't change how much you earn that day. However, if you move money out of a high-yield account into a low-yield account, you'll earn less interest going forward because your balance in the high-yield account is lower.

What's the difference between APY and interest rate?

The interest rate is the percentage the bank pays on your balance. APY (annual percentage yield) includes the effect of compounding, so it's always slightly higher than the stated interest rate. Banks are required to show you the APY, which is the number to use when comparing accounts.