Interest is money the bank pays you for keeping your money there

When you deposit money into a savings account, the bank lends that money out to other customers as mortgages, car loans, and business loans. In return, the bank pays you interest — a percentage of your balance that gets added to your account on a set schedule, usually monthly or daily. The rate the bank pays you is called the Annual Percentage Yield (APY), and it tells you how much you'll earn in a year if you don't withdraw anything.

The amount of interest you earn depends on three things: how much money you have in the account, what APY the bank is offering, and how long the money sits there. A $10,000 balance at 4.5% APY earns more than a $1,000 balance at the same rate. A bank offering 4.5% APY pays more than one offering 0.01% APY. And money that stays in the account for a full year earns more than money withdrawn after three months.

Interest is not the same as a bonus. A bonus is a one-time payment the bank makes when you open an account or meet a condition like setting up direct deposit. Interest keeps accumulating as long as your money stays in the account.

Key Takeaways

  • Interest is money the bank pays you for holding your deposits, calculated as a percentage of your balance called the Annual Percentage Yield (APY).
  • The interest you earn depends on your account balance, the APY rate, and how long the money stays in the account.
  • Most banks calculate and add interest to your account monthly or daily, though the frequency varies by institution.
  • High-yield savings accounts at online banks typically pay 4% to 5% APY, while traditional brick-and-mortar banks often pay less than 0.5% APY.
  • Interest rates change over time and are set by each bank independently, so comparing rates across banks before opening an account matters.

How the bank calculates and adds interest to your account

Banks use one of two methods to calculate interest: simple interest or compound interest. With simple interest, the bank calculates what you earn based only on your starting balance. With compound interest — which is what most savings accounts use — the bank calculates interest on your balance plus any interest you've already earned. Compound interest means you earn "interest on interest," which grows your money faster over time.

The bank decides how often to compound interest: daily, monthly, or quarterly. Daily compounding is the most common for savings accounts and works in your favor because interest gets calculated and added more frequently. If your account compounds daily, you start earning interest on yesterday's interest today. If it compounds monthly, you wait 30 days before that happens.

You can see how often your bank compounds interest in the account's disclosure document, usually called the Truth in Savings Act disclosure or account terms. The APY already factors in how often compounding happens, so you don't have to do the math yourself — the APY is what you'll actually earn if you leave the money untouched for a year.

Why APY varies so much between banks

The Federal Reserve sets a benchmark interest rate that influences what banks pay, but each bank decides its own APY independently. Online banks typically pay higher APY than traditional banks because they have lower overhead costs — no physical branches, fewer employees, lower rent. A high-yield savings account at an online bank might pay 4.5% APY while a brick-and-mortar bank pays 0.15% APY on the same type of account.

Banks also change their rates based on market conditions and how much money they need to attract. When the Federal Reserve raises its benchmark rate, banks usually raise their APY to stay competitive. When the benchmark falls, banks lower their rates. Some banks move quickly; others lag behind by weeks or months.

The APY you see advertised is the rate for new customers, and it can change at any time. Banks are required to notify you before lowering your rate, but they can raise it without notice. Check your bank's website or call to confirm the current rate before opening an account, because rates posted online can be outdated.

The difference between APY and APR

APY (Annual Percentage Yield) and APR (Annual Percentage Rate) sound similar but mean different things. APY includes the effect of compound interest and tells you what you'll actually earn. APR does not include compounding and is used mainly for loans and credit cards, not savings accounts.

If a bank advertises an APY of 4.5%, that's the real amount you'll earn in a year if you don't touch the money. If you see APR mentioned for a savings account, that's a red flag — the bank should be using APY instead. Always look for APY when comparing savings accounts.

How much interest you'll actually earn

You can estimate your earnings with a simple formula: multiply your balance by the APY, then divide by 12 for a monthly estimate. A $10,000 balance at 4.5% APY earns roughly $37.50 per month (before taxes). A $50,000 balance at the same rate earns roughly $187.50 per month.

These are rough estimates because the actual amount depends on exactly when interest is calculated and added, and whether your balance changes during the month. If you deposit money mid-month, you won't earn interest on that deposit until the next calculation period. If you withdraw money, your balance drops and so does your interest.

Your bank will send you a statement each month showing how much interest was added. You can also log into your online account and see the interest posted in real time on most banks' websites.

Interest and taxes

Interest you earn on a savings account is taxable income. At the end of each year, your bank will send you a Form 1099-INT if you earned $10 or more in interest during the year. You report this interest on your federal tax return, and depending on your state, you may also owe state income tax on it.

The more interest you earn, the more you owe in taxes. This is one reason why high-yield savings accounts matter — earning 4.5% instead of 0.15% means more interest to report, but also significantly more money in your pocket even after taxes. If you earned $450 in interest at 4.5% APY, you'd owe roughly $90 to $135 in federal taxes (depending on your tax bracket), leaving you with $315 to $360 in actual gain.

When interest rates are falling or rising

Interest rates move in cycles. When the Federal Reserve raises its benchmark rate, banks eventually raise what they pay on savings accounts — though sometimes with a delay of weeks or months. When the benchmark falls, banks lower their rates quickly, sometimes within days.

If you're earning 4.5% APY today and rates fall to 2%, your bank will lower your rate too. You won't lose the interest you've already earned, but future interest will be calculated at the lower rate. This is why locking in a high rate matters: if you open a high-yield account when rates are high, you benefit from that rate for as long as you keep the money there, even if rates drop later.

Conversely, if rates are rising and you're in a low-rate account, you can move your money to a bank offering a higher rate. There's no penalty for switching banks, and you'll start earning more interest immediately at the new institution.

Frequently Asked Questions

Do I have to pay taxes on savings account interest?

Yes. Interest is taxable income. Your bank reports it to the IRS on Form 1099-INT if you earn $10 or more per year. You report it on your tax return and pay federal income tax on it, plus state income tax if your state has one. The amount you owe depends on your tax bracket.

Can a bank lower my interest rate without warning?

Banks can lower your rate, but they must notify you first — usually by mail or email. They cannot lower your rate without telling you. However, they can raise your rate without notice. Always check your email and statements for rate change notices from your bank.

What's the difference between a savings account and a money market account?

Both earn interest, but money market accounts often pay slightly higher rates in exchange for requiring a larger minimum balance and limiting how many withdrawals you can make per month. Savings accounts are more flexible. Both are insured by the FDIC up to $250,000.

Does interest compound if I withdraw money before the year ends?

Yes, but only on the money that stays in the account. If you deposit $10,000 and withdraw $3,000 after six months, you earn interest on the full $10,000 for those six months, then on $7,000 for the remaining six months. The APY assumes a full year, so withdrawing early means you earn less than the advertised rate.

Why do online banks pay more interest than regular banks?

Online banks have lower costs because they don't operate physical branches or employ as many staff. They pass those savings to customers by paying higher interest rates on savings accounts. Traditional banks need to cover the cost of buildings and employees, so they pay less interest.