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 to other customers through mortgages, car loans, and business lines of credit. In exchange, the bank pays you interest — a percentage of your balance, calculated and added to your account on a schedule set by the bank. The rate you earn depends on the account type, the bank's current rates, and sometimes how much you have deposited.

The bank's interest rate is not fixed forever. It changes based on what the Federal Reserve does with its benchmark rate, which it adjusts several times a year. When the Fed raises rates, banks typically raise the rates they pay on savings accounts within weeks or months. When the Fed cuts rates, savings rates usually fall too. This is why the interest you earn today may be different from what you earn six months from now.

You do not have to do anything to earn interest. Once your money is in the account, the bank calculates and deposits the interest automatically on the schedule they use — usually daily, monthly, or quarterly.

Key Takeaways

  • Banks pay interest as a percentage of your account balance, and that percentage changes when the Federal Reserve adjusts its benchmark rate.
  • Interest is calculated on a daily, monthly, or quarterly schedule depending on the bank, and the frequency affects how much you earn over time.
  • Compound interest means the bank pays interest on your interest, so your balance grows faster the longer money sits in the account.
  • The interest rate you see advertised is the annual percentage yield (APY), which already accounts for how often interest is compounded.

How the bank calculates the interest you earn

The bank uses a formula based on three things: your account balance, the interest rate, and how often interest is compounded. Compounding means the bank pays interest on the interest you have already earned, not just on your original deposit.

Here is a concrete example. Suppose you have $10,000 in a savings account earning 4.5% APY, and the bank compounds interest daily. On day one, the bank calculates one day's worth of interest on $10,000 and adds it to your account — roughly $1.23. On day two, the bank calculates interest on $10,001.23, not just the original $10,000. That extra $1.23 now earns interest too. This compounds every single day for a year, which is why the total interest you earn is slightly more than a straightforward 4.5% of $10,000.

The annual percentage yield (APY) is the rate the bank advertises because it already includes the effect of compounding. If a bank shows you 4.5% APY, that is the actual return you will see over a year, assuming the rate does not change and you do not withdraw money.

The difference between daily, monthly, and quarterly compounding

Banks compound interest on different schedules. The most common are daily, monthly, and quarterly. Daily compounding means the bank recalculates and adds interest to your balance every single day. Monthly compounding happens once a month. Quarterly compounding happens four times a year.

The more often interest compounds, the more you earn, because you earn interest on your interest more frequently. The difference is usually small — on a $10,000 balance at 4.5% APY, daily compounding might earn you roughly $450 over a year, while monthly compounding might earn you roughly $449. But over years or with larger balances, the difference adds up.

You can find the compounding schedule in the account disclosure document the bank provides, usually called the Truth in Savings disclosure or the account agreement. It will state exactly when interest is calculated and posted to your account.

When the bank actually deposits interest into your account

The bank calculates interest on a daily or monthly basis, but it does not always deposit it that frequently. Many banks calculate interest daily but deposit it only once a month. Some deposit quarterly. A few deposit annually.

The timing matters because you only start earning interest on that deposited amount once it hits your account. If a bank calculates interest daily but deposits it only at the end of the month, you do not earn interest on that interest until the next month begins. This is why the compounding frequency (how often it is calculated) and the posting frequency (how often it is added to your balance) are two separate things, and both appear in your account agreement.

You can see when interest was actually posted by looking at your account statement or transaction history. It usually appears as a single line item labeled "interest paid" or "interest deposited" on the day the bank added it.

How changes in the Federal Reserve rate affect what you earn

The Federal Reserve does not set the interest rate your bank pays you. But it does set the federal funds rate, which is the rate banks charge each other for overnight loans. When the Fed raises this rate, banks raise the rates they pay on savings accounts to attract deposits. When the Fed cuts the rate, banks typically cut savings rates too.

The lag between a Fed rate change and a change to your account rate is usually two to eight weeks. Some banks move faster than others. A few banks raise rates quickly but cut them slowly — this is not illegal, and it is worth comparing rates across banks if you are concerned about it.

Your bank will notify you of a rate change, usually by email or through your online account portal. The notification will state the new rate and when it takes effect. If you have a promotional rate that was may provide for a certain period, that rate does not change until the promotional period ends, even if the Fed moves.

Why some accounts earn more interest than others

Different account types earn different rates. High-yield savings accounts typically earn two to four times more than standard savings accounts at the same bank. Money market accounts often earn rates between standard savings and high-yield savings. Certificates of deposit (CDs) usually earn the highest rates, but you have to lock your money away for a set period.

Online banks usually offer higher rates than brick-and-mortar banks because they have lower overhead costs. A standard savings account at a large national bank might earn 0.01% APY, while a high-yield account at an online bank might earn 4.5% APY. The difference on a $10,000 balance is roughly $1 per year versus $450 per year.

Some banks also offer tiered rates, where you earn more interest if your balance is higher. For example, balances under $25,000 might earn 3.5% APY, while balances over $100,000 earn 4.5% APY. The account agreement will spell out the exact tiers and rates.

What happens to interest if you withdraw money mid-month

If you withdraw money before the bank deposits interest, you lose the interest that would have been calculated on that withdrawn amount. The interest is calculated on your balance at the time of calculation, so a withdrawal reduces the balance used in the next calculation.

Some banks use the average daily balance method, which calculates interest based on your average balance over the month rather than your balance on a single day. This method is slightly more forgiving if you withdraw mid-month, because the interest is spread across the entire period. Other banks use the daily balance method, which calculates interest on your exact balance each day. With daily balance, a withdrawal when ready reduces the next day's interest calculation.

Your account agreement will state which method the bank uses. You can also call the bank or check your online account to see how they calculate interest on your specific account type.

Frequently Asked Questions

Does interest get taxed?

Yes. Interest earned in a savings account is taxable income. The bank will send you a Form 1099-INT 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 in taxes depends on your overall income and tax bracket.

Can I lose money if interest rates fall?

No. Your account balance itself does not go down if rates fall. You straightforward earn less interest going forward. If you have $10,000 and rates drop from 4.5% to 2.0%, you still have $10,000, but you will earn roughly $200 per year instead of $450. Your principal is never at risk in a savings account.

What is the difference between APY and APR?

APY (annual percentage yield) is what banks use for savings accounts and includes the effect of compounding. APR (annual percentage rate) is what lenders use for loans and credit cards and does not include compounding. For savings, always look at the APY, because that is the actual return you will see.

Does my interest earn interest?

Yes, if the bank compounds interest. The interest deposited to your account in month one earns interest in month two, and so on. This is why compounding frequency matters — the more often interest is compounded, the more your interest earns interest.

What if my bank goes out of business?

Your deposits and any accrued interest are protected up to $250,000 per account type by the Federal Deposit Insurance Corporation (FDIC) if your bank is FDIC-insured. Most banks are. You can check on the FDIC website to confirm your bank's coverage.