Interest is money the bank pays you for keeping your money there

When you deposit money into a savings account, the bank uses that money to lend to other customers. In exchange, the bank pays you interest — a percentage of your balance that gets added to your account on a regular schedule, usually monthly or daily. The more money you keep in the account and the higher the interest rate, the more interest you earn.

The interest rate itself is set by the bank and varies depending on the type of account, current market conditions, and how much competition exists among banks in your area. Some accounts offer rates near zero; others offer rates between 4% and 5% annually. The rate can change at any time, especially for accounts that don't lock in a fixed rate.

Interest compounds, meaning you earn interest on your interest. If your account earns interest monthly, the interest added in month one becomes part of your balance in month two, and you earn interest on that larger amount. Over time, compounding makes your money grow faster than simple addition would suggest.

Key Takeaways

  • Banks pay you interest as a percentage of your account balance, usually calculated daily but added monthly or quarterly.
  • The interest rate varies by bank and account type, and can change without notice unless you have a fixed-rate account.
  • Compound interest means you earn interest on the interest already added to your account, which accelerates growth over time.
  • Higher balances and longer holding periods result in more total interest earned, but the rate the bank offers matters more than how long you wait.
  • You can compare rates across banks before opening an account, and switching to a higher-rate account may be worth the effort if the difference is significant.

How the bank calculates the interest you earn

The bank uses a formula based on three things: your account balance, the annual interest rate (called the APY or Annual Percentage Yield), and how often interest is added to your account. Most banks calculate interest daily but deposit it monthly, quarterly, or annually.

Here is a concrete example. Suppose you have $10,000 in an account with a 4.5% APY, and the bank adds interest monthly. The bank divides the annual rate by 12 to get the monthly rate (0.375%), then multiplies that by your balance ($10,000 × 0.00375 = $37.50). After one month, $37.50 is added to your account. In month two, the calculation uses $10,037.50 as the new balance, so you earn slightly more interest. This is compounding in action.

The exact timing matters. Some banks calculate interest based on your lowest balance during the month; others use your average balance or your ending balance. Read the account terms to see which method your bank uses, because it changes how much you actually earn.

Why interest rates change and what affects them

Banks set their savings rates based on what the Federal Reserve does with its benchmark interest rate. When the Fed raises rates, banks usually raise savings rates too, because they can borrow money more cheaply and want to attract deposits. When the Fed cuts rates, savings rates typically fall.

Competition also drives rates. During periods when many banks are competing for deposits, rates climb. When deposits are plentiful and banks don't need more money, rates drop. Online banks often offer higher rates than brick-and-mortar banks because they have lower overhead costs and can pass savings to customers.

The type of account also matters. A regular savings account usually earns less interest than a money market account or a certificate of deposit (CD), because those accounts have restrictions on how often you can withdraw money. The bank rewards you for leaving your money untouched longer by offering a higher rate.

Fixed rates versus rates that can change

Most savings accounts have variable rates, meaning the bank can change the rate at any time without notice. You might open an account at 4.5% and see it drop to 3.2% six months later if the Fed cuts rates or the bank decides to lower its offer.

Some accounts, particularly certificates of deposit (CDs), lock in a fixed rate for a set period — typically three months to five years. If you open a CD at 5% for one year, you earn 5% for the full year no matter what happens to other rates. The trade-off is that you cannot withdraw the money without paying a penalty, usually a loss of some or all of the interest you have earned.

If you want to lock in a rate before it drops, a CD is the tool to use. If you want flexibility to move your money or take advantage of rising rates, a variable-rate savings account is better, even if the current rate is lower.

How to compare interest rates across banks

Before opening a savings account, check the APY offered by at least three banks. Online banks, credit unions, and traditional banks all publish their current rates on their websites. The APY is the number to compare, not the "interest rate," because APY includes the effect of compounding and shows you the true annual return.

A difference of 1% may not sound large, but it compounds significantly over time. On a $10,000 balance, the difference between 3% and 4% is $100 per year. Over five years with compounding, the gap widens to more than $500. For larger balances or longer time horizons, the difference is even bigger.

Also check whether the bank charges monthly fees, requires a minimum balance, or limits the number of withdrawals per month. A high interest rate is less valuable if fees eat into your earnings or if restrictions prevent you from accessing your money when you need it.

What happens to interest if you withdraw money

When you withdraw money from a savings account, the interest you have already earned stays in your account. The interest you earn going forward is calculated on the smaller remaining balance. If you withdraw $5,000 from a $10,000 account, next month's interest is based on $5,000, not $10,000.

Some accounts penalize frequent withdrawals. Federal law allows banks to limit savings account withdrawals to six per month; if you exceed that, the bank can charge a fee or close your account. Money market accounts and CDs have stricter withdrawal limits. If you think you will need to access your money regularly, a regular savings account is better than a CD, even if the rate is lower.

If you withdraw money before a CD matures, you pay an early withdrawal penalty, which is usually a certain number of months' worth of interest. A CD with a 5% APY and a three-month penalty means you lose three months of interest if you cash out early. Read the CD terms before you buy to understand the penalty.

How interest affects your taxes

Interest you earn on a savings account is taxable income. The bank will send you a Form 1099-INT at the end of the year showing how much interest you earned. You report this on your tax return, and you owe federal income tax on it at your regular tax rate.

Some states also tax savings account interest, though the amount varies. If you live in a state with income tax, check whether savings interest is taxed and at what rate. A few states exempt interest income below a certain threshold, so the tax impact may be small if you earn only a few dollars in interest.

The tax you owe reduces the real return on your savings. If you earn $500 in interest and owe 24% in federal tax, you keep $380 and pay $120 to the IRS. This is why the actual money in your pocket is less than the interest rate alone would suggest.

Frequently Asked Questions

How often does interest get added to my account?

Most banks calculate interest daily but add it to your account monthly, quarterly, or annually. Check your account agreement to see the schedule. Daily calculation means you earn interest on every dollar every day, even if it is only added once a month. The more frequently interest is added, the more you benefit from compounding.

Can I lose money in a savings account?

No. The Federal Deposit Insurance Corporation (FDIC) insures savings accounts up to $250,000 per depositor per bank, so your principal is protected even if the bank fails. You will not earn much interest in a very low-rate environment, but you will not lose what you deposited. Credit unions offer similar protection through the National Credit Union Administration (NCUA).

Is it better to move my money to a higher-rate account?

If the rate difference is 1% or more and your balance is large enough that the extra interest covers any switching costs, moving makes sense. Calculate how much extra interest you would earn in a year at the new rate, then decide if it is worth the time to open a new account and transfer funds. For small balances under $5,000, the difference may not justify the effort.

What is the difference between APY and APR?

APY (Annual Percentage Yield) includes compounding and shows the true annual return on a savings account. APR (Annual Percentage Rate) does not include compounding and is used for loans and credit cards. Always compare APY when shopping for savings accounts, because it reflects what you actually earn.

Do I have to pay taxes on interest if I earn very little?

Yes, you report all interest income on your tax return, even if it is only a few dollars. However, if your total interest is under $10, the bank may not send you a Form 1099-INT. You still owe tax on it, but the amount is usually small enough that it does not change your tax bill significantly.