Your interest depends on the bank's rate, how much you deposit, and how long you leave the money there

The amount of interest you earn in a savings account is determined by three things: the annual percentage yield (APY) the bank offers, the balance you keep in the account, and the time your money sits there. A bank offering 4.5% APY on $10,000 will pay you roughly $450 per year—but only if that $10,000 stays in the account for the full year. A bank offering 0.01% APY on the same $10,000 will pay you about $1 per year. The difference between these two scenarios is real money, and it matters which bank you choose.

Interest is calculated daily or monthly depending on the bank, but paid out monthly or quarterly. You don't have to do anything to receive it—the bank deposits it directly into your account. The catch is that most banks change their rates frequently, sometimes weekly. A rate that is 4.5% today might be 4.0% next month. This means the interest you earn in January might be different from what you earn in February, even if your balance stays the same.

Key Takeaways

  • Interest earned equals the APY rate multiplied by your account balance, divided by 365 days (or 360, depending on the bank's method).
  • Banks change savings rates often—sometimes weekly—so the rate you see today may not be the rate you earn next month.
  • Online banks typically offer higher APY than brick-and-mortar banks because they have lower overhead costs.
  • Money market accounts and certificates of deposit (CDs) often pay more interest than regular savings accounts, but with different rules about when you can withdraw.

How the math actually works

Banks calculate interest using a straightforward formula: your balance multiplied by the APY, divided by the number of days in a year. If you have $5,000 in an account earning 4.5% APY, the bank divides 4.5% by 365 days, then multiplies that daily rate by your $5,000 balance. That gives you roughly $0.62 per day in interest. Over a full year, that adds up to about $225.

The timing matters. If you deposit $5,000 on January 15 and withdraw it on February 15, you earn interest for only 31 days, not 365. That same account earning 4.5% APY would pay you roughly $19 instead of $225. Banks calculate this daily, so every day your money sits there, you earn a small amount. The longer it stays, the more you accumulate.

Some banks use 360 days instead of 365 to calculate interest. This is legal and actually works in the bank's favor—it slightly reduces what you earn. Always check whether your bank uses 360 or 365 days. It is a small difference on small balances, but on $100,000 or more, it can add up to several dollars per year.

Why rates vary so much between banks

Online banks almost always pay more interest than traditional banks with physical branches. A major national bank might offer 0.01% APY on savings, while an online bank offers 4.5% APY on the same type of account. The difference is overhead. A brick-and-mortar bank pays for buildings, staff, and ATM networks. An online bank has none of that. They pass the savings to customers through higher rates.

Banks also change rates based on what the Federal Reserve does. When the Fed raises its benchmark interest rate, banks raise savings rates. When the Fed cuts rates, banks cut savings rates—sometimes within days. This is why a rate that was 5.0% in July might be 4.5% by October. You have no control over this, but you can move your money to a different bank if rates drop too far.

Competition matters too. When many banks offer similar high rates, it is because they are competing for deposits. When rates are low across the board, it usually means the Fed has cut rates and banks are not competing as hard. Checking rates at multiple banks before you deposit takes five minutes and can mean hundreds of dollars in difference over a year.

Comparing savings accounts to other options

A regular savings account is the most flexible option—you can withdraw your money anytime without penalty. But flexibility costs you. Money market accounts often pay slightly higher interest than savings accounts, though they may require a higher minimum balance (sometimes $2,500 or more). You can still withdraw money, but the account may limit you to six withdrawals per month.

Certificates of deposit (CDs) pay the highest interest rates because you agree to lock your money away for a set time—three months, six months, one year, or longer. If you withdraw before the term ends, you pay a penalty that eats into your interest earnings. A one-year CD might pay 5.0% APY, while a savings account pays 4.5% APY. That extra 0.5% is the bank's way of compensating you for not being able to touch the money.

High-yield savings accounts are a middle ground. They pay rates similar to or better than money market accounts, with the same flexibility as a regular savings account. Most online banks offer high-yield savings accounts. If you need your money to stay accessible, a high-yield savings account usually beats a regular savings account at any traditional bank.

What happens to interest if you make deposits or withdrawals

Interest is calculated on your daily balance, so deposits and withdrawals change how much you earn. If you start January with $10,000 and deposit another $5,000 on January 15, the bank calculates interest on $10,000 for 14 days, then on $15,000 for the remaining 17 days of January. This is called the average daily balance method, and most banks use it.

Some banks use the minimum balance method instead—they calculate interest based on the lowest balance you held during the month. If you had $10,000 on January 1, withdrew $5,000 on January 15, and redeposited it on January 31, the bank would calculate interest on $5,000 for the entire month, even though you had $10,000 for most of it. This method pays you less. Check your bank's method before you open an account.

Withdrawals work the same way. If you withdraw $5,000 mid-month, you stop earning interest on that $5,000 from that day forward. The interest you already earned stays in your account, but future interest is calculated on the lower balance. This is why moving money between accounts can cost you—you lose a few days of interest each time.

How inflation affects what your interest actually buys you

Interest is only useful if it outpaces inflation. If your savings account earns 1.0% APY but inflation is running at 3.0% per year, you are actually losing purchasing power. Your $10,000 grows to $10,100, but that $10,100 buys less than your original $10,000 would have bought a year ago.

This is why the difference between a 0.01% savings account and a 4.5% high-yield savings account matters. At 0.01%, you are almost certainly losing money to inflation. At 4.5%, you are keeping pace with or beating inflation in most years. Check what inflation is running at—the Bureau of Labor Statistics publishes this monthly—and compare it to the APY your bank is offering. If the APY is lower than inflation, your money is shrinking in real terms.

Frequently Asked Questions

Do I have to pay taxes on savings account interest?

Yes. Interest earned in a savings account is taxable income. Your bank will send you a 1099-INT form at the end of the year if you earned $10 or more in interest. You report this on your tax return. The amount you owe depends on your tax bracket. If you earn $500 in interest and you are in the 24% tax bracket, you owe roughly $120 in taxes on that interest.

Can I lose money in a savings account?

No, as long as your bank is insured by the FDIC (Federal Deposit Insurance Corporation). The FDIC protects up to $250,000 per account holder per bank. Your balance will not shrink due to bank failure. However, inflation can reduce what your money buys, which is a different kind of loss.

What if I move my money to a different bank mid-year?

You keep all the interest you earned up to the day you withdraw. The old bank calculates interest through your withdrawal date. The new bank starts calculating interest the day your deposit clears. You do not lose any interest by switching banks, though you may miss a few days of interest during the transfer.

Is there a minimum balance to earn interest?

It depends on the bank. Some banks pay interest on any balance, even $1. Others require a minimum balance of $500, $1,000, or more. If your balance falls below the minimum, some banks stop paying interest entirely. Check your bank's terms before you open an account.

How often is interest added to my account?

Banks calculate interest daily but usually deposit it monthly or quarterly. Some banks deposit it more frequently. Check your account statement or bank website to see when interest posts. The frequency does not change how much you earn over a year—it only changes when you see the money in your account.