What determines how much interest you earn

The amount of interest your savings account earns 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. The bank sets the APY, which varies by institution and changes over time. You earn interest on your balance, so a $5,000 account earning 4.5% APY generates different dollars than a $500 account at the same rate.

Interest compounds, meaning you earn interest on your interest. Most savings accounts compound daily or monthly. If your account compounds daily, the bank calculates interest each day on your full balance (including any interest already added), then adds it all up at the end of the month. This matters more the longer your money sits in the account.

The Federal Reserve sets a benchmark interest rate that influences what banks offer. When the Fed raises rates, banks typically raise their savings APY within weeks. When the Fed cuts rates, savings APY falls. This is why the same account might pay 4.5% one year and 2.0% the next—not because the bank changed its terms, but because the broader rate environment shifted.

Key Takeaways

  • Your interest earnings equal your account balance multiplied by the APY, divided by 365 days, then compounded daily or monthly depending on the bank.
  • APY varies widely between banks—a high-yield savings account might pay 4.5% while a traditional bank pays 0.01%, earning you hundreds of dollars more per year on the same balance.
  • Interest compounds, so money that sits longer generates more total dollars because you earn returns on your returns.
  • The APY your bank offers changes when the Federal Reserve adjusts its benchmark rate, usually within one to four weeks.

How to calculate what you'll actually earn

The formula is straightforward: Balance × APY ÷ 365 = annual interest. If you have $10,000 in an account paying 4.5% APY, you earn roughly $450 per year. Divide that by 12 and you earn about $37.50 per month.

This assumes your balance stays constant. If you add money throughout the year, the calculation becomes more complex because each deposit earns interest for a different length of time. Most banks show you the projected interest in your online account dashboard, which accounts for your actual balance and compounding schedule.

The difference between banks is substantial. A $25,000 balance earning 4.5% APY generates $1,125 per year. The same $25,000 at 0.01% APY (typical at large national banks) earns $2.50 per year. Over five years, that's a difference of $5,612.50 in your pocket.

Why APY varies so much between banks

Online banks and credit unions typically offer higher APY than traditional brick-and-mortar banks. Online banks have lower overhead costs—no physical branches, fewer employees—so they pass some of that savings to customers through higher rates. A bank like Marcus or Ally might offer 4.5% APY while Chase or Bank of America offers 0.01% on the same type of account.

Banks also use savings rates as a tool to attract deposits. When a bank needs more customer money to lend out, it raises its APY to compete. When it has plenty of deposits, it may lower rates. This is why you see APY change even when the Federal Reserve hasn't moved its benchmark rate.

Account type matters too. Money market accounts sometimes pay slightly more than savings accounts. Certificates of deposit (CDs) lock your money away for a set term—three months, one year, five years—and typically pay more than savings accounts because the bank knows it can use your money for that full period without you withdrawing it.

How compounding increases your earnings over time

Compounding is the reason $10,000 earning 4.5% APY doesn't straightforward earn $450 per year forever. In year one, you earn $450. In year two, you earn 4.5% on $10,450 (your original balance plus the interest), which is $470.25. By year five, your balance is $12,462.82 and you've earned $2,462.82 total—not just $2,250.

The longer your money stays in the account, the more compounding works in your favor. After 10 years at 4.5% APY with no deposits or withdrawals, $10,000 becomes $15,530.69. After 20 years, it becomes $24,117.14. The second decade generates more dollars than the first because you're earning interest on a larger balance.

Daily compounding beats monthly compounding, which beats annual compounding, though the difference is small on typical savings balances. On $10,000 at 4.5% APY, daily compounding earns you about $2 more per year than annual compounding. On $100,000, the difference is closer to $20 per year.

What happens when interest rates change

When the Federal Reserve raises its benchmark rate, banks usually increase their savings APY within one to four weeks. The increase is not automatic—banks decide how much of the Fed's rate increase to pass along to savers. Some banks raise rates quickly and fully; others raise them slowly or partially.

When the Fed cuts rates, banks cut savings APY faster and more aggressively than they raised it. A bank might take a month to raise rates by 0.5% but cut rates by 0.5% within a week. This is why savers should lock in high rates when they're available—rates can fall quickly.

Your existing balance earns the new rate when ready. You don't have to do anything. If your bank drops its APY from 4.5% to 3.5%, every dollar in your account starts earning at the lower rate right away. This is why some savers move money to banks with higher rates when their current bank cuts rates.

Comparing savings accounts to find the best rate

The best way to compare is to check the current APY on sites that track rates across multiple banks. Bankrate, DepositAccounts, and the banks' own websites all show current rates. Look for the APY, not the interest rate—APY includes compounding and is the true annual return you'll receive.

Check whether the rate applies to all balances or only balances above a certain amount. Some banks pay 4.5% on balances up to $100,000 and 2.0% on anything above that. Others pay the same rate on all balances. Read the fine print about minimum balance requirements and whether the bank charges monthly fees that would eat into your interest.

Consider the bank's stability and whether your deposits are insured. The Federal Deposit Insurance Corporation (FDIC) insures deposits up to $250,000 per depositor per bank. Credit union deposits are insured by the National Credit Union Administration (NCUA) up to the same amount. If a bank fails, your money is protected up to the limit.

Interest on different types of savings accounts

A traditional savings account at a large national bank typically pays 0.01% to 0.05% APY. A high-yield savings account at an online bank typically pays 4.0% to 5.0% APY. A money market account falls somewhere in between, often paying 3.5% to 4.5% APY, though it may require a higher minimum balance.

Certificates of deposit (CDs) usually pay more than savings accounts because your money is locked away. A three-month CD might pay 4.5% APY, a one-year CD might pay 5.0%, and a five-year CD might pay 4.75%. The longer the term, the more the bank can count on having your money, but rates don't always increase with longer terms—sometimes they decrease.

Money market accounts often come with a debit card and check-writing privileges, making them more flexible than savings accounts but less flexible than checking accounts. The trade-off is that they may require a higher minimum balance—sometimes $2,500 or more—to earn the advertised APY.

Frequently Asked Questions

How often does interest get added to my account?

Most banks compound interest daily but credit it (add it to your balance) monthly. This means interest is calculated each day on your full balance, but you see the total added once a month. Some banks credit interest quarterly or annually. Check your account agreement or call the bank to confirm the schedule.

Do I pay taxes on savings account interest?

Yes. Interest earned on a savings account is taxable income. The bank sends you a 1099-INT form each January if you earned $10 or more in interest during the year. You report this on your tax return. The amount you owe in taxes depends on your tax bracket.

What's the difference between APY and interest rate?

Interest rate is the percentage the bank pays on your balance. APY is the annual percentage yield, which includes the effect of compounding. APY is always equal to or higher than the interest rate because it accounts for interest earned on interest. Always compare APY, not interest rate, when choosing between accounts.

Can I lose money in a savings account?

Your principal balance cannot go down due to interest rates or market changes—savings accounts are not investments. However, if your bank charges monthly fees and your interest doesn't cover them, your balance shrinks. This is rare at online banks but common at traditional banks. Read the fee schedule before opening an account.

What happens to my interest if I withdraw money mid-month?

Most banks calculate interest on your average daily balance. If you withdraw money partway through the month, you earn interest only on the balance for the days you held it. Some banks use the lowest balance method, paying interest only on your smallest balance during the period, which is less favorable to you.