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 loans. The bank keeps the difference between what it pays you and what borrowers pay them. That payment to you is interest.
The bank calculates your interest based on three things: how much money you have in the account, the interest rate the bank offers, and how long your money sits there. The longer your balance stays in the account and the higher the rate, the more interest you earn.
Interest is real money that appears in your account. You can withdraw it, spend it, or leave it there to earn interest on top of itself—a process called compounding.
Key Takeaways
- Banks pay you interest because they use your deposits to make loans to other customers.
- Your interest earnings depend on your account balance, the interest rate, and how long the money stays deposited.
- Interest compounds, meaning you earn interest on your interest, which makes your money grow faster over time.
- Banks calculate and add interest on different schedules—daily, monthly, or quarterly—and the frequency affects how much you earn.
- High-yield savings accounts and money market accounts typically pay much more interest than traditional savings accounts at the same bank.
How the bank calculates the dollar amount you earn
The bank uses a formula based on your balance and the annual percentage yield, or APY. The APY is the interest rate expressed as a yearly number. If an account offers 4.50% APY and you have $10,000 in it for a full year with no deposits or withdrawals, you would earn roughly $450 in interest (though the exact amount depends on how often the bank compounds, explained below).
You do not earn that $450 all at once. The bank divides the annual rate by the number of times it compounds per year. If it compounds daily, it divides 4.50% by 365, calculates interest on your balance that day, and adds a tiny amount to your account. The next day it does the same thing on your new, slightly larger balance.
If your balance changes—you deposit $5,000 or withdraw $2,000—the bank recalculates. Your interest is always based on whatever balance you actually have on each calculation day.
What compounding means and why it matters
Compounding is earning interest on the interest you already earned. After the bank adds your first day's interest to your account, your new balance is slightly higher. The next day's interest calculation uses that higher balance, so you earn a tiny bit more interest. This repeats every day, week, or month depending on the account.
Over time, compounding creates a snowball effect. Your money grows faster than it would if you only earned interest on your original deposit. A $10,000 deposit earning 4.50% APY compounded daily will grow to roughly $10,460 after one year. The same $10,000 earning 4.50% with no compounding would only grow to $10,450.
The difference seems small in one year, but it compounds over decades. Money left untouched in a savings account for 20 years at 4.50% APY compounded daily grows to roughly $24,600. That extra $4,600 came entirely from compounding—earning interest on interest.
How often banks compound interest
Banks compound interest on different schedules. Some compound daily, some weekly, some monthly, and some quarterly. The more often a bank compounds, the more interest you earn, because you earn interest on your interest more frequently.
Daily compounding is the most common for savings accounts and produces the highest earnings. Weekly and monthly compounding are less common. Quarterly compounding is rare for savings accounts but appears on some certificates of deposit, or CDs.
The difference between daily and monthly compounding is small on modest balances, but it grows with larger amounts and longer time periods. When you compare savings accounts, the APY already accounts for the compounding frequency, so you can compare rates directly without doing the math yourself.
Why interest rates vary between banks and account types
Banks set their own interest rates based on what the Federal Reserve charges them to borrow money and what they can earn by lending to customers. When the Federal Reserve raises its rates, banks eventually raise savings account rates. When it lowers rates, banks lower them too, though usually with a delay.
Online banks typically pay higher interest rates than brick-and-mortar banks because they have lower overhead costs—no physical branches to maintain, fewer employees, lower rent. A traditional bank might pay 0.01% APY on a regular savings account while an online bank pays 4.00% or higher on the same type of account.
Account type also matters. A regular savings account at any bank pays less than a high-yield savings account at the same bank. Money market accounts usually pay more than savings accounts. CDs usually pay more than money market accounts because your money is locked in for a set period.
The difference between APY and APR
APY stands for annual percentage yield. APR stands for annual percentage rate. For savings accounts, you want to look at APY, not APR. APY includes the effect of compounding, while APR does not.
APR is used for loans and credit cards—things where you owe money. APY is used for savings accounts and CDs—things where the bank owes you money. If a savings account shows both numbers, the APY will always be higher because it accounts for compounding.
Banks are required to display APY prominently when advertising savings rates, so you will see it on their website and in account disclosures. Use APY to compare accounts at different banks.
What happens to your interest if you withdraw money early
If you withdraw money from a savings account before the interest is credited, you lose the interest on that amount. The bank calculates interest based on your balance on each compounding day. If you had $10,000 on Monday and withdrew $5,000 on Wednesday, the interest credited on Friday is calculated as if you only had $5,000 for part of the week.
Regular savings accounts have no penalty for withdrawals. You can take money out whenever you want. CDs are different—they have a set term, like 6 months or 1 year, and withdrawing early triggers a penalty, usually a loss of some or all of the interest you earned.
High-yield savings accounts and money market accounts also allow withdrawals without penalty, though some banks limit how many withdrawals you can make per month.
How to find accounts with the highest interest rates
Interest rates change constantly. The rate your bank offers today may be different next month. To find the highest-paying accounts, check rate comparison websites that track savings accounts, money market accounts, and CDs across multiple banks. These sites update rates regularly and let you filter by account type and term length.
Online banks almost always offer higher rates than traditional banks. If you have accounts at a brick-and-mortar bank, compare their rates to what online banks are offering. The difference can be substantial—sometimes 3% or 4% higher at an online bank.
Read the account details carefully. Some banks offer a promotional rate for the first few months, then drop the rate significantly. Others offer high rates only on balances above a certain amount. Make sure the rate you see is the ongoing rate for your balance level, not a temporary promotion.
Frequently Asked Questions
Do I have to pay taxes on interest I earn?
Yes. Interest earned in a savings account is taxable income. Banks 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 tax bracket.
Can interest rates go down after I open an account?
Yes. Banks can lower their interest rates at any time for new deposits and existing accounts. If rates drop, your earnings will be lower going forward. This is why some people move money to different banks when rates change—to find the highest rate available.
What's the difference between a savings account and a money market account?
Money market accounts usually pay higher interest than savings accounts at the same bank. In exchange, they often require a larger minimum balance and may limit how many withdrawals you can make per month. Both are safe because deposits are insured by the FDIC up to $250,000.
How long does it take to see interest in my account?
Interest is usually credited monthly or quarterly, depending on the bank. You will see it appear as a deposit in your account on the crediting date. Some banks credit interest daily but only show it in your statement monthly. Check your account details to see when interest is credited.
Is there a minimum balance to earn interest?
It depends on the bank and account type. Some savings accounts pay interest on any balance, even $1. Others require a minimum balance, like $500 or $1,000, to earn the advertised rate. If your balance falls below the minimum, you might earn a lower rate or no interest at all. Check the account terms before opening.