Interest is how your savings account balance increases
Your money grows in a savings account through interest—a percentage of your balance that the bank adds to your account on a regular schedule. The bank pays you this interest because they use your deposited money to lend to other customers. The amount you earn depends on three things: how much money you have in the account, what interest rate the bank offers, and how often the bank compounds the interest (adds it back into your balance so it earns interest too).
The interest rate varies widely between banks and account types. A savings account at a large national bank might offer 0.01% annual interest, while an online bank's high-yield savings account might offer 4.5% or higher. The difference is real money: on $10,000, the first account earns about $1 per year, while the second earns roughly $450 per year. Banks set their rates based on what the Federal Reserve does with interest rates, so rates change over time.
You do not have to do anything to earn interest. Once you open the account and deposit money, the bank automatically calculates and adds interest according to its schedule—usually monthly or daily. You can watch your balance grow by checking your account online or through your bank's app.
Key Takeaways
- Interest is money the bank pays you based on your account balance, expressed as an annual percentage rate (APY).
- High-yield savings accounts at online banks typically offer much higher rates than traditional bank savings accounts, sometimes 4% or more versus 0.01%.
- Compound interest means interest gets added to your balance and then earns interest itself, making your money grow faster over time.
- Your earnings depend on the rate, your balance, and how often interest compounds—daily compounding grows your money faster than monthly.
- Interest rates change when the Federal Reserve adjusts its rates, so what you earn today may be different in six months.
How compound interest makes your balance grow faster
Compound interest is interest that earns interest. When the bank adds interest to your account, that interest becomes part of your new balance. The next time interest is calculated, it is calculated on the larger balance—which includes the interest you already earned. This creates a snowball effect where your money grows faster and faster.
The difference between simple and compound interest is small at first but grows over years. If you deposit $5,000 at 4% annual interest compounded daily, after one year you will have about $5,204. After five years, you will have about $6,104. If the interest were simple (not compounded), you would only have $6,000 after five years. The compounding added $104 extra.
How often the bank compounds matters. Daily compounding grows your money faster than monthly compounding, which grows faster than annual compounding. Most online banks compound daily, while some traditional banks compound monthly or quarterly. When you compare accounts, look for the APY (Annual Percentage Yield), which already accounts for compounding and shows you the real rate of growth.
Real examples of how different rates affect your money
The following table shows how $10,000 grows over five years at different interest rates, all compounded daily. These are realistic rates you can find at actual banks today, though rates change frequently.
| Interest Rate (APY) | Balance After 1 Year | Balance After 5 Years | Total Interest Earned |
|---|---|---|---|
| 0.01% (typical large bank) | $10,001 | $10,005 | $5 |
| 1.0% (moderate online bank) | $10,100 | $10,513 | $513 |
| 4.5% (high-yield online bank) | $10,460 | $12,461 | $2,461 |
The difference between 0.01% and 4.5% is $2,456 over five years on the same $10,000. That is why where you keep your money matters. Moving your savings to a higher-rate account costs nothing and takes a few minutes, but the growth is substantial.
Why interest rates change and what that means for you
Banks do not set interest rates on their own. The Federal Reserve sets a target range for the federal funds rate, which is the interest rate banks charge each other for overnight loans. When the Fed raises its rate, banks typically raise the rates they offer on savings accounts. When the Fed lowers its rate, savings account rates usually fall too.
This means the interest rate you see today may not be the rate you earn next year. If you open a high-yield savings account at 4.5% APY, that rate is not locked in forever. The bank can lower it whenever the Fed lowers its rate or whenever the bank decides to be less competitive. Some banks lower rates quickly; others wait longer. You can always move your money to a different bank if rates drop too far.
The opposite is also true: if rates rise, you may be able to move your money to a bank offering a higher rate. Checking your account's current rate once or twice a year and comparing it to what other banks offer takes a few minutes and can save you money over time.
How to calculate your own interest earnings
If you want to know exactly how much interest you will earn, you can use a savings calculator or do the math yourself. The formula for compound interest is: A = P(1 + r/n)^(nt), where A is your final amount, P is your starting balance, r is the annual interest rate as a decimal, n is how many times per year interest compounds, and t is the number of years.
For example, if you deposit $5,000 at 4% APY compounded daily for two years: A = 5000(1 + 0.04/365)^(365×2) = $5,416.66. Your interest earned is $416.66. Most banks and financial websites have online calculators that do this for you—you just enter your balance, rate, and time period, and the calculator shows you the result.
You can also check your actual earnings by looking at your account statements. Banks are required to show you how much interest was added each month or quarter. If the number seems low compared to the rate they advertised, double-check the APY and make sure you are comparing the right numbers.
What happens to your interest if you withdraw money early
Withdrawing money from a savings account does not trigger a penalty or stop your interest from growing. You can take money out whenever you want, and the interest you already earned stays in your account. However, your interest earnings going forward will be based on your new, lower balance.
If you have $10,000 earning 4% APY and you withdraw $5,000, you still keep the interest you earned on the full $10,000 up to that point. But from that day forward, interest is calculated only on the remaining $5,000. This is different from a Certificate of Deposit (CD), which does charge a penalty if you withdraw before the term ends—but savings accounts have no such restriction.
Frequently Asked Questions
Is the interest I earn on a savings account taxed?
Yes. Interest income is taxable as ordinary income on your federal tax return. Banks send you a 1099-INT form each January showing how much interest you earned the previous year. The amount you owe in taxes depends on your tax bracket. If you earned $500 in interest and you are in the 22% tax bracket, you owe roughly $110 in federal tax on that interest.
Can I lose money in a savings account?
No. Your deposits are protected by the FDIC (Federal Deposit Insurance Corporation) up to $250,000 per account holder per bank. Your balance will not go down unless you withdraw money yourself. Interest rates can fall, which means you earn less, but your principal is safe.
How often should I check my interest rate to see if I should switch banks?
Checking once or twice a year is reasonable. If your current rate drops below 3% and other banks are offering 4% or higher, moving your money takes about 15 minutes and could earn you hundreds of dollars per year. There is no penalty for switching banks, so it is worth doing when the rate difference is significant.
Does keeping more money in the account earn more interest?
Yes. Interest is calculated as a percentage of your balance, so a larger balance earns more. If you have $1,000 at 4% APY, you earn about $40 per year. If you have $10,000 at the same rate, you earn about $400 per year. The percentage stays the same, but the dollar amount grows with your balance.
What is the difference between APR and APY?
APR (Annual Percentage Rate) does not include compounding, while APY (Annual Percentage Yield) does. For savings accounts, always look at the APY because it shows the real rate of growth after compounding is factored in. APR is more commonly used for loans and credit cards.