Interest is money the bank pays you for letting them use your deposits

When you put money in a savings account, the bank lends that money out to other customers as mortgages, car loans, and business credit lines. In return, the bank pays you interest—a percentage of your balance, calculated and added to your account on a schedule the bank sets. The more you deposit and the longer you leave it there, the more interest you earn. The rate the bank offers you depends on what the Federal Reserve is doing with interest rates, how much competition exists in your area, and what type of account you open.

Interest is not a refund or a government payment. It is income the bank generates from lending your money, and they share a portion of that income with you. You do not have to do anything to receive it—the bank calculates it automatically and deposits it into your account.

Key Takeaways

  • Banks pay interest as a percentage of your account balance, and the rate varies by bank, account type, and current economic conditions.
  • Interest is calculated daily or monthly but usually posted to your account only once per month, so you may not see it immediately.
  • A higher annual percentage yield (APY) means more money in your pocket over time, especially if you compare accounts before opening one.
  • Interest rates change when the Federal Reserve adjusts its benchmark rate, so the rate your bank pays you today may be different in six months.
  • Online banks typically offer higher interest rates than brick-and-mortar banks because they have lower operating costs.

How banks calculate the interest you earn

Banks use your annual percentage yield, or APY, to calculate how much interest you make in a year. The APY is expressed as a percentage—for example, 4.50% or 0.01%. To find out how much you will earn in a month, the bank divides the APY by 12. If your APY is 4.50%, your monthly rate is roughly 0.375%.

The bank then multiplies your account balance by that monthly rate to find the interest owed to you for that month. If you have $10,000 in the account and the monthly rate is 0.375%, you earn about $37.50 that month. The calculation happens every day at most banks, but the interest is usually added to your account only once per month, often on the last day of the month or the first day of the next month.

Some banks calculate interest daily and post it daily; others calculate daily but post monthly. A few older banks calculate and post monthly. The difference is small for most people, but daily calculation means you earn a tiny bit more because interest starts accruing the moment you deposit money, rather than waiting until the next posting date.

The difference between APY and interest rate

You may see two numbers listed for a savings account: the interest rate and the APY. The interest rate is the raw percentage the bank pays. The APY includes the effect of compounding—the process of earning interest on your interest.

Here is how compounding works: In month one, you earn interest on your original deposit. In month two, you earn interest on your original deposit plus the interest you earned in month one. That extra interest on interest is small each month, but it adds up over years. The APY is always equal to or higher than the interest rate because it reflects this compounding effect. When you compare savings accounts, always look at the APY, not the interest rate, because the APY tells you the true amount you will earn.

Why interest rates change and what affects yours

The Federal Reserve, the central bank of the United States, sets a benchmark interest rate that influences what all banks pay on savings accounts. When the Federal Reserve raises its rate, banks usually raise the rates they pay on savings accounts within weeks or months. When the Federal Reserve lowers its rate, banks lower savings rates too, often faster than they raise them.

Beyond the Federal Reserve's actions, individual banks set their own rates based on how much money they need to attract, how much they are paying to borrow money themselves, and how much they can earn by lending that money out. Online banks often pay higher rates than traditional banks because they do not have the cost of maintaining physical branches. Banks in areas with many competitors may pay higher rates to attract deposits. A bank that has plenty of deposits may lower its rate because it does not need to attract more money.

Your rate can also change based on the type of account. A money market account may pay a higher rate than a basic savings account. A certificate of deposit (CD) locks in a rate for a set period—three months, one year, five years—and that rate does not change, even if the Federal Reserve moves rates up or down.

How often interest is added to your account

Most banks calculate interest daily but add it to your account monthly. A few add it quarterly (every three months) or annually (once a year). The posting schedule matters because you do not earn interest on money until it is actually in your account. If your bank posts interest on the last day of the month and you withdraw money on the 15th, you will not earn interest on the withdrawn amount for the second half of the month.

When interest is posted, it becomes part of your balance and starts earning interest itself in the next calculation period. This is compounding in action. Over many years, monthly compounding earns noticeably more than annual compounding, especially at higher rates. If you are comparing two accounts with the same APY but different posting schedules, the one that posts more frequently will earn you slightly more money.

What to look for when comparing savings accounts

The APY is the most important number, but it is not the only one. Check whether the bank requires a minimum deposit to open the account or to earn the advertised rate. Some banks offer a high rate only if you deposit $25,000 or more; others have no minimum. Look at the monthly fee, if any. A $10 monthly fee on a $5,000 account earning 4% APY will wipe out most of your interest income.

Also check how often interest is posted and whether the bank is FDIC-insured. FDIC insurance means the federal government guarantees your deposits up to $250,000 if the bank fails. Nearly all banks are FDIC-insured, but it is worth confirming. Finally, look at the bank's website or call to see whether the rate is fixed or variable. A fixed rate stays the same for a set period; a variable rate can change at any time, usually when the Federal Reserve moves rates.

How inflation affects what your interest earnings are worth

Interest earnings are real money added to your account, but inflation—the rising cost of goods and services over time—can reduce what that money can buy. If your savings account earns 4% APY but inflation is running at 3%, your money is gaining purchasing power at roughly 1% per year. If inflation is 5% and your account earns 4%, you are actually losing purchasing power, even though the dollar amount in your account is growing.

This does not mean you should avoid savings accounts. They are safe, insured, and liquid—you can access your money whenever you need it. But it is worth understanding that in a high-inflation environment, the interest you earn may not keep pace with rising prices. High-yield savings accounts, which currently offer rates around 4% to 5%, perform better in this situation than traditional savings accounts, which often pay less than 0.5%.

Frequently Asked Questions

Do I have to pay taxes on savings account interest?

Yes. Interest earned on a savings account is taxable income. Banks 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 of tax you owe depends on your overall income and tax bracket.

Can a bank lower my interest rate without warning?

Yes. Banks can change variable interest rates at any time without notice. If you want a rate that will not change, open a certificate of deposit (CD), which locks in a rate for a specific period. Savings account rates are almost always variable.

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

Interest is calculated on your balance at the time the calculation happens. If you withdraw money before interest is posted, you lose interest on that withdrawn amount for that period. Some banks use the average daily balance method, which averages your balance over the month, so withdrawals mid-month reduce interest proportionally.

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

No. There is no cap on interest earnings. The more you deposit and the longer you leave it, the more interest you earn. However, FDIC insurance only covers up to $250,000 per depositor per bank, so if you have more than that, consider spreading deposits across multiple banks.

Why do online banks pay more interest than my current bank?

Online banks have lower overhead costs because they do not maintain physical branches or employ as many staff. They pass those savings to customers by offering higher interest rates. They also compete aggressively for deposits because they cannot rely on local foot traffic. The tradeoff is that you cannot walk into a branch to deposit cash or speak to someone in person.