How interest works on a savings account

A bank pays you interest as a percentage of the money you keep in your account. The bank uses your deposits to lend money to other customers and businesses, then shares a small portion of what it earns back to you. The amount you receive depends on three things: how much money sits in your account, what annual percentage yield (APY) the bank offers, and how often the bank compounds the interest—meaning how often it adds earned interest back into your balance so you earn interest on that interest too.

Most savings accounts compound interest daily or monthly. If your account compounds daily, the bank calculates what you've earned each day and adds it to your balance. The next day, you earn interest on that larger balance. Over time, this compounding effect makes your money grow faster than if the bank simply paid you once a year. The exact amount you receive depends entirely on the bank's rate and compounding schedule, which can change at any time.

Key Takeaways

  • Interest is calculated as a percentage of your account balance, and the rate your bank offers can change whenever the bank decides to change it.
  • Daily compounding means the bank adds interest to your balance every day, so you earn interest on interest, which accelerates growth over months and years.
  • A higher APY means more money in your pocket, so comparing rates between banks before opening an account can add up to hundreds of dollars over time.
  • You only earn interest on money that actually sits in the account; withdrawals reduce your balance and the interest you receive that period.
  • Some accounts charge monthly fees that reduce or eliminate the interest you earn, so the true return is the APY minus any fees.

The difference between APY and interest rate

Banks advertise two different numbers: the interest rate and the annual percentage yield (APY). The interest rate is the raw percentage the bank pays on your balance. The APY includes that rate plus the effect of compounding over a full year. Because of compounding, the APY is always equal to or higher than the interest rate—sometimes noticeably higher if the account compounds daily.

When you compare accounts, always look at the APY, not the interest rate. A bank might advertise a 4.50% interest rate that compounds daily, which could equal a 4.60% APY. Another bank might offer a 4.55% interest rate that compounds monthly, which might equal 4.65% APY. The second bank's APY is higher, so you'd earn more money there even though the interest rate looks lower. Banks are required to show you the APY when you open an account, so you can compare apples to apples.

How the bank calculates what you earn

The bank uses a formula to calculate daily interest. It takes your account balance, multiplies it by the daily interest rate (the APY divided by 365), and that gives you the interest earned that day. If your account compounds daily, that amount gets added to your balance at the end of the day. The next day, the calculation starts over using your new, slightly larger balance.

Here's a concrete example: if you have $10,000 in an account with a 4.50% APY that compounds daily, the daily interest rate is 4.50% ÷ 365, or about 0.0123% per day. On day one, you earn roughly $1.23. That gets added to your balance, so on day two you earn interest on $10,001.23. The difference is tiny each day, but over a year, daily compounding adds up to noticeably more than if the bank paid interest once at the end of the year.

If your account compounds monthly instead, the bank waits 30 days, calculates all the interest you've earned that month, and adds it all at once. Monthly compounding means you earn less total interest than daily compounding, because your balance doesn't grow as quickly between payments.

When banks pay interest and how you receive it

Most banks add interest to your account automatically on a schedule—daily, weekly, monthly, or quarterly, depending on the account. You don't have to do anything to receive it. The interest simply appears in your balance. Some banks show interest deposits as separate line items in your transaction history; others roll it into your balance without a separate line. Either way, the money is yours to keep or withdraw.

You'll receive a statement—either monthly or quarterly, depending on the bank—that shows how much interest you earned that period. This statement is important for tax purposes. At the end of the calendar year, if you earned $10 or more in interest, the bank will send you a Form 1099-INT, which you'll need when you file your taxes. The interest you earn is taxable income, even though you didn't work for it.

Why interest rates change and what that means for you

Banks set their own interest rates and can change them whenever they want. Most banks raise rates when the Federal Reserve raises its benchmark rate, and lower rates when the Fed cuts. However, banks don't always move at the same speed or by the same amount. Some banks raise rates quickly; others lag behind. Some banks lower rates immediately when the Fed cuts; others hold their rates steady for a while.

If you lock in a high rate now, that rate is not may provide to stay the same. Banks can lower your rate at any time, though they usually give you notice first. If rates drop and you want to keep earning more, you may need to move your money to a different bank. This is why it's worth checking rates every few months—if your current bank's rate falls significantly behind competitors, switching accounts could earn you hundreds of dollars more per year on the same balance.

How fees reduce the interest you actually keep

Some savings accounts charge monthly maintenance fees, overdraft fees, or fees for falling below a minimum balance. These fees come directly out of your account and reduce the interest you earn. If an account offers a 4.50% APY but charges a $5 monthly fee, you're losing $60 per year. On a $10,000 balance, the 4.50% APY would earn you $450, but the $60 in fees cuts that down to $390 actual earnings.

Before opening a savings account, read the fee schedule carefully. Many online banks and credit unions offer savings accounts with no monthly fees and no minimum balance requirements. These accounts let you keep every penny of interest you earn. If your current bank charges fees and competitors don't, switching could be worth your time.

How your balance affects how much interest you earn

Interest is calculated on your actual balance, so the more money you keep in the account, the more interest you earn. If you have $1,000 at 4.50% APY, you'll earn about $45 per year. If you have $10,000 at the same rate, you'll earn about $450 per year. The rate stays the same, but the dollar amount grows with your balance.

This also means that withdrawals reduce your interest earnings. If you deposit $5,000 on the first of the month and withdraw $2,000 on the fifteenth, the bank calculates interest on the average balance or the daily balance, depending on the account terms. Either way, you earn less interest that month than if you'd left the full $5,000 untouched. Some people keep a separate checking account for everyday spending and leave their savings account alone to maximize interest earnings.

Frequently Asked Questions

Can I lose money in a savings account because of interest rates?

No. Interest only adds to your balance; it never subtracts. However, if inflation rises faster than your interest rate, the purchasing power of your money decreases over time. If you earn 2% interest but inflation is 4%, your money is worth less in real terms, even though the account balance is higher.

What happens to my interest if I close the account?

You keep all interest you've already earned. When you close the account, the bank pays out your full balance, including all accumulated interest, to you. Interest stops accruing the day you close the account.

Do I pay taxes on savings account interest?

Yes. Interest income is taxable. If you earn $10 or more in a calendar year, the bank sends you a Form 1099-INT in January, and you report that income on your tax return. Interest earned in a regular savings account is taxed at your ordinary income tax rate.

Is there a limit to how much interest I can earn?

No. There's no cap on interest earnings. The more money you keep in the account and the higher the APY, the more interest you earn. Some accounts do have maximum balance limits for certain promotional rates, so check the terms before depositing large amounts.

Why do some banks offer much higher interest rates than others?

Online banks typically offer higher rates than brick-and-mortar banks because they have lower overhead costs. Credit unions sometimes offer competitive rates to members. Banks also use high rates to attract new deposits. Rates vary based on the bank's funding needs and business model, not on the safety of your money—all deposits up to $250,000 are insured by the FDIC regardless of the rate.