Interest is money the bank pays you for letting them use your money
When you put money in a savings account, the bank takes that money and lends it to other customers — for mortgages, car loans, credit cards, and business loans. The bank charges those borrowers interest, which is a fee for using the money. The bank keeps most of that fee, but shares a portion with you as a reward for depositing your money there in the first place. That share is your account interest.
The amount you earn depends on two things: how much money you have in the account, and the interest rate the bank is currently offering. The interest rate is a percentage — for example, 4.5% per year. If you have $1,000 in an account earning 4.5% annual interest, the bank will pay you roughly $45 over the course of a year (the exact amount varies slightly depending on how the bank calculates it).
Interest rates change constantly. Banks raise them when they need to attract more deposits, and lower them when they have enough money on hand. You might open an account at 4.5%, but six months later that same bank might only offer 3.8% to new customers. Your existing money usually keeps earning at the rate you started with, unless the bank changes the terms of your account.
Key Takeaways
- Interest is the bank's payment to you for keeping your money in their account, calculated as a percentage of your balance.
- The amount you earn each month or year depends on your account balance and the interest rate your bank is offering.
- Interest rates vary by bank and change frequently, so comparing rates before opening an account can mean earning significantly more.
- Most banks add interest to your account monthly or daily, though the timing and method varies by institution.
How banks calculate and add interest to your account
Banks use one of two main methods to calculate interest: straightforward interest or compound interest. With straightforward interest, the bank calculates your earnings based only on the money you originally deposited. With compound interest, the bank calculates earnings on your original deposit plus any interest you have already earned. Compound interest means you earn "interest on your interest," which grows your balance faster over time.
Most savings accounts use compound interest, and most compound it daily or monthly. Daily compounding is better for you because interest gets calculated and added more frequently, which means your balance grows slightly faster. When the bank compounds interest daily, it divides your annual interest rate by 365, calculates what you earned that day, and adds it to your account. The next day, it calculates interest on the new, slightly larger balance.
You will see this interest appear in your account as a deposit. Some banks add it on the last day of each month, others on the last day of the quarter (every three months), and some add it daily but only show you the total once a month on your statement. Check your account agreement or ask your bank when and how often interest is added to your specific account.
Why interest rates are different at different banks
Banks set their own interest rates based on what the Federal Reserve is doing and what other banks are offering. The Federal Reserve (the central bank of the United States) sets a target interest rate that influences how much banks charge borrowers. When the Fed raises its rate, banks usually raise the interest they pay on savings accounts. When the Fed lowers its rate, banks usually lower what they pay you.
Beyond that, banks compete for deposits. A bank that needs more customer deposits might offer a higher interest rate to attract them. A bank that already has plenty of deposits might offer a lower rate. Online banks — which have lower costs because they do not operate physical branches — often offer higher interest rates than traditional banks with many locations.
This is why it matters to compare rates before opening an account. The difference between a 4.5% rate and a 2.0% rate is substantial over time. On $10,000, that difference means earning roughly $250 more per year. Over five years, the gap grows much larger because of compounding.
The difference between APY and interest rate
Banks advertise savings accounts using a term called APY, which stands for Annual Percentage Yield. This is different from the interest rate itself. The interest rate is the percentage the bank pays, but APY includes the effect of compounding. If a bank compounds interest daily, the APY will be slightly higher than the stated interest rate because you are earning interest on your interest.
When you are comparing accounts at different banks, always compare the APY, not the interest rate. The APY tells you the real amount you will earn over a year. Two banks might advertise similar interest rates, but if one compounds daily and the other compounds monthly, the one that compounds daily will have a higher APY and will actually pay you more.
What happens to interest when you withdraw money
If you withdraw money from your savings account before the end of the month or quarter, you typically lose the interest you would have earned on that withdrawn amount. For example, if you have $5,000 in your account on the first day of the month, but withdraw $2,000 on the 15th, the bank usually calculates interest only on the $3,000 that remained for the full period.
Some banks use a method called the "average daily balance," which calculates interest based on how much money you had in the account each day of the month, then averages those daily amounts. This method is slightly more favorable to you if you withdraw money mid-month, because you earn interest on the money for the days it was there. Ask your bank which method they use.
This is one reason savings accounts are designed for money you do not plan to touch regularly. If you need to withdraw money frequently, you earn less interest because your balance is lower more often.
How inflation affects what your interest actually buys you
Inflation is the general rise in prices over time. When inflation is high, the money in your savings account buys less than it used to. If your savings account earns 2% interest but inflation is 4%, you are actually losing purchasing power — your money is worth less in real terms, even though the account balance went up.
This is why comparing interest rates to inflation matters. When interest rates are high relative to inflation, your savings account is a good place to keep money you want to protect. When interest rates are low relative to inflation, you might want to explore other options, though most people new to banking should focus on building an emergency fund in a savings account first, regardless of the rate.
You cannot control inflation or interest rates, but you can control which bank you choose. Picking a bank with a higher interest rate means your money works harder for you, even if that rate is still lower than inflation.
Frequently Asked Questions
Do I have to do anything to earn interest, or does it happen automatically?
Interest happens automatically. Once you open a savings account and deposit money, the bank begins calculating and adding interest according to the account terms. You do not need to take any action. You will see the interest appear as deposits on your statement.
Can interest rates go down on my existing account?
Yes. Banks can lower the interest rate on your account at any time, though they usually must notify you in advance (the notice period varies by bank). If your rate drops and you are unhappy, you can move your money to a different bank offering a higher rate.
What is the difference between a savings account and a money market account for interest?
Money market accounts often offer slightly higher interest rates than regular savings accounts, but they usually require a larger minimum balance and limit how many withdrawals you can make per month. Both earn interest automatically. For most people new to banking, a regular savings account is simpler to manage.
Is the interest I earn taxed?
Yes. Interest income is considered taxable income by the IRS. If you earn more than a small amount (the threshold changes yearly), your bank will send you a form called a 1099-INT that you report on your tax return. Keep track of your interest earnings throughout the year.
Why is my interest so small if the rate seems high?
Interest is calculated on your account balance, so a high rate on a small balance still produces small earnings. A 4.5% rate on $500 earns about $22.50 per year. As your balance grows, the interest grows too. This is why building up your savings over time matters.