Banks pay interest by calculating a percentage of your balance and crediting that amount to your account on a set schedule

Interest is money the bank pays you for letting them use your deposit. The bank lends your money to other customers through mortgages, car loans, and business loans. They keep some of the interest those borrowers pay, and they give some back to you. The amount you receive depends on three things: how much money you have in the account, the interest rate the bank offers, and how often the bank calculates and adds the interest to your balance.

The process is straightforward in practice. You deposit $1,000. The bank looks at your balance on a specific day each month (or quarter, or year, depending on the account). They multiply your balance by the interest rate, divide by the number of times per year they pay interest, and add that amount to your account. That's it. You don't have to do anything. The money appears automatically.

Key Takeaways

  • Banks calculate interest based on your account balance, the interest rate they offer, and how often they compound — usually daily, monthly, or quarterly.
  • The interest rate varies by bank and account type, and it changes over time based on what the Federal Reserve does with its benchmark rate.
  • Compound interest means the bank pays interest on your interest, so your balance grows faster the longer money sits in the account.
  • You can compare interest rates across banks before opening an account, and some banks pay significantly more than others for the same type of account.
  • Interest is taxable income, and the bank will send you a tax form (1099-INT) if you earn more than a small amount in a year.

The three numbers that determine how much interest you earn

Your account balance is the amount of money sitting in the account on the day the bank calculates interest. If you have $5,000 in the account, that's the number they use. If you withdraw $500 the day before they calculate, they use $4,500. Some banks calculate interest based on your average balance over the month instead of the balance on one specific day, which can work in your favor if you tend to withdraw money near the end of the month.

The interest rate is the percentage the bank will pay you. A bank might offer 4.5% annual percentage yield (APY) on a savings account. That means if you had exactly $1,000 in the account for a full year and earned no other interest, you would have $1,045 at the end. The rate varies from bank to bank — some online banks pay 4% or higher, while traditional brick-and-mortar banks might pay 0.01%. The rate also changes over time. When the Federal Reserve raises its benchmark interest rate, banks usually raise the rates they pay on savings accounts within weeks or months. When the Fed lowers rates, banks lower theirs too.

How often the bank compounds interest means how many times per year they calculate and add interest to your balance. This is where compound interest comes in. If a bank compounds daily, they calculate interest 365 times per year. If they compound monthly, they calculate 12 times. If they compound quarterly, they calculate 4 times. The more often they compound, the more interest you earn, because you earn interest on the interest from the previous calculation.

How compound interest works in your favor

Compound interest is interest paid on interest. Here's a concrete example. Say you have $10,000 in an account that pays 4% APY, compounded monthly. In month one, the bank calculates 4% divided by 12 (which is about 0.33%) and applies it to your $10,000. You earn about $33. Your new balance is $10,033. In month two, they calculate 0.33% of $10,033, not $10,000. You earn about $33.11. The extra penny came from earning interest on the $33 you earned in month one.

Over a year, this compounds to real money. With $10,000 at 4% APY compounded monthly, you would have about $10,407 after one year. If the bank only paid straightforward interest (no compounding), you would have exactly $10,400. The difference is small with one year and one account, but it grows larger the longer your money sits there and the higher the interest rate.

This is why the annual percentage yield (APY) matters more than the stated interest rate. APY already includes the effect of compounding, so it tells you the real amount you'll earn in a year. When you compare savings accounts at different banks, always compare APY to APY, not the raw interest rate.

When and how the interest lands in your account

The bank adds interest to your account on a schedule they set. Most banks compound daily but credit interest monthly — meaning they calculate interest every day, but they add the total to your balance once a month. Some add it quarterly (four times a year). A few add it annually (once a year). The schedule is in the account's terms and conditions, which the bank must give you before you open the account or when you request it.

You'll see the interest appear as a deposit in your account history. It usually shows up on the same day each month, or within a few days. You don't have to do anything to receive it. Once it's in your account, it's yours to keep, spend, or leave there to earn more interest.

Why interest rates differ between banks and account types

Banks set their own interest rates based on what they think they can afford to pay and still make a profit. Online banks typically pay higher rates than traditional banks because they have lower overhead costs — no physical branches, fewer employees, less real estate. They pass some of that savings to customers in the form of higher interest rates.

Different account types also pay different rates. A regular savings account might pay 0.5% APY, while a money market account at the same bank might pay 1.5%. A certificate of deposit (CD) — an account where you agree to leave money untouched for a set period — usually pays more than a savings account because the bank knows it can use that money for longer. The tradeoff is that you can't withdraw from a CD without a penalty.

Interest rates also move with the broader economy. When the Federal Reserve raises its benchmark rate, banks have more incentive to pay higher rates on savings accounts because they can charge more on loans. When the Fed lowers rates, banks lower what they pay savers. This happens gradually over weeks or months, not overnight.

How to find out what your bank is paying you

Your bank must disclose the interest rate and APY before you open an account. You can find this information on the bank's website, in the account disclosure document (sometimes called a "Truth in Savings" form), or by calling the bank. The disclosure also tells you how often interest is compounded and when it's credited to your account.

Once you have an account, you can see how much interest you've earned by looking at your account statement. Most banks show interest as a separate line item. You can also log into your online banking portal and check your balance and transaction history. If you earned more than $10 in interest during the year, the bank will send you a 1099-INT tax form by January 31 of the following year. You'll need this form to file your taxes.

If you want to compare what different banks are paying, websites like Bankrate, DepositAccounts, and the FDIC's BankFind tool let you search by account type and see current rates. Rates change frequently, so check before you open an account if getting the highest rate matters to you.

Interest is taxable income

The interest you earn on a savings account is considered income by the IRS, and you have to report it on your tax return. If you earned $10 or more in interest during the year, the bank sends you a 1099-INT form. If you earned less than $10, the bank doesn't have to send the form, but you still have to report the interest on your taxes.

The amount of tax you owe depends on your overall income and tax bracket. If you're in a higher tax bracket, you'll owe more tax on the interest. This is one reason some people keep money in high-yield savings accounts rather than letting it sit in a checking account earning nothing — the interest, even after taxes, is better than zero.

Frequently Asked Questions

Can I move money between banks to earn more interest?

Yes. There's no penalty for moving your savings to a bank that pays a higher rate. You can withdraw from one bank and deposit at another. The only thing to watch is whether your original bank charges a fee for closing the account, though most don't. If you're moving a large amount, ask both banks about their deposit limits and how long transfers take.

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

It depends on when the bank calculates interest. If they calculate on the last day of the month and you withdraw on the 15th, you'll still earn interest on the full balance for that month because the calculation hasn't happened yet. If you withdraw after the calculation, you won't earn interest on the money you withdrew. Check your account terms to see when your bank calculates interest.

Do I have to do anything to earn interest?

No. Once you open the account and deposit money, the bank automatically calculates and credits interest on the schedule they set. You don't have to sign anything, make requests, or take any action. The interest appears in your account on its own.

Why do some banks pay almost no interest?

Traditional banks with physical branches often pay very low rates (0.01% or less) because they don't need to attract deposits — they have steady customers and lower costs than online banks. Online banks and credit unions typically pay higher rates because they compete for deposits and have lower overhead. If you're earning almost nothing, moving to a different bank could significantly increase your interest without any risk to your money.

Is my interest protected if the bank fails?

Yes. The FDIC (Federal Deposit Insurance Corporation) insures deposits up to $250,000 per account holder per bank. This means if the bank fails, you get your money back, including any interest that was credited to your account. Interest that was calculated but not yet credited is also covered.