What determines how much interest you earn
The amount of interest you earn depends on three things: how much money sits in the account, what annual percentage yield (APY) the bank offers, and how long the money stays there. A bank with a 4.5% APY will pay you more than one offering 0.01% APY on the same balance. The difference between two accounts can mean hundreds of dollars a year on a $10,000 deposit.
Banks set their own APY rates and change them whenever they want. When the Federal Reserve raises its benchmark interest rate, banks typically raise savings APY within days or weeks. When rates fall, banks lower APY much more slowly—sometimes not at all. This is why shopping around matters: two banks in the same week might offer 4.75% and 0.50% on identical account types.
The bank also decides how often it compounds interest—daily, monthly, or quarterly. Daily compounding means you earn interest on your interest more frequently, which adds up over time. Most online banks compound daily. The difference between daily and monthly compounding on $10,000 at 4.5% APY is roughly $1 per year, so it matters less than the APY itself, but it still works in your favor.
Key Takeaways
- Interest earned = your balance × APY ÷ 365 days (or the number of days the money was in the account).
- A 4% APY account earns roughly $400 per year on a $10,000 balance; a 0.5% APY account earns roughly $50 on the same balance.
- Banks change APY rates without notice, so the rate you see today may be lower next month.
- Online banks typically offer higher APY than brick-and-mortar banks because they have lower overhead costs.
- Daily compounding adds slightly more interest than monthly or quarterly compounding, but APY is the bigger factor in what you earn.
How to calculate interest on your own balance
The basic formula is: balance × APY ÷ 365 = interest earned per day. If you have $5,000 in an account with 4.5% APY, you earn roughly $0.62 per day ($5,000 × 0.045 ÷ 365). Over a year, that's about $226.
Banks don't pay you all at once. They calculate daily interest and deposit it monthly or quarterly, depending on the account. When you see your statement, the interest has already been added to your balance. If you leave the money untouched, next month's interest calculation includes both your original balance and the interest you just earned—that's compounding.
Your actual earnings may differ slightly from the formula because banks use different methods to count days. Some use 360 days instead of 365. Some calculate interest only on the lowest balance during the month rather than the average balance. Read the account disclosure or call the bank to confirm which method they use.
Why online banks pay more than traditional banks
Online banks typically offer 4% to 5% APY on savings accounts, while brick-and-mortar banks often offer 0.01% to 0.5%. The difference is cost. Online banks have no physical branches, no tellers, and no building leases. They pass those savings to customers by paying higher interest rates. They still make money by lending out deposits at higher rates than they pay you.
Traditional banks keep APY low because they rely on other revenue: overdraft fees, monthly maintenance fees, and loan origination fees. They don't need to attract deposits with high interest rates because customers come for the branch locations and the brand name. If you're willing to bank online, you can earn 8 to 10 times more interest on the same balance.
Some credit unions also offer competitive APY, especially on savings accounts for members who meet certain requirements (like maintaining a minimum balance or setting up direct deposit). Check your local credit union's rates alongside online banks.
How interest rates change and when to move your money
The Federal Reserve sets a benchmark rate that influences what banks pay on savings. When the Fed raises rates, banks raise APY within days. When the Fed cuts rates, banks cut APY slowly—sometimes weeks or months later. This creates windows where one bank's rate is noticeably higher than others.
You don't have to stay with a bank that lowers its rate. Moving money to a higher-paying account takes one to three business days via ACH transfer. There's no penalty for moving savings between banks. If your current bank drops from 4.5% to 3.5% APY and another bank is offering 4.75%, the difference on $50,000 is roughly $625 per year. That's worth the transfer.
Set a calendar reminder to check rates every three to six months. Websites like Bankrate, DepositAccounts, and the banks' own websites show current APY. Compare the rate you're earning to what's available elsewhere. If you're earning less than 3.5% on a savings account in an environment where 4.5% is available, you're leaving money on the table.
Interest earned on different account balances
| Balance | At 0.5% APY | At 2.5% APY | At 4.5% APY |
|---|---|---|---|
| $1,000 | $5 per year | $25 per year | $45 per year |
| $5,000 | $25 per year | $125 per year | $225 per year |
| $10,000 | $50 per year | $250 per year | $450 per year |
| $50,000 | $250 per year | $1,250 per year | $2,250 per year |
| $100,000 | $500 per year | $2,500 per year | $4,500 per year |
What happens to interest if you withdraw money mid-month
If you withdraw money before the bank calculates and deposits interest, you lose the interest you would have earned on that amount. If you have $10,000 earning 4.5% APY and withdraw $5,000 on the 15th of the month, the bank calculates interest only on the $5,000 that remained for the full period (or on an average balance, depending on the bank's method).
Some banks calculate interest daily and deposit it monthly, so you earn interest on every dollar for every day it sits in the account. Others calculate interest on the lowest balance during the month, which penalizes you for withdrawals. Read your account agreement or ask the bank which method they use before you open the account.
High-yield savings accounts are designed for money you won't touch. If you need to withdraw regularly, the interest you earn is smaller anyway, so the account type matters less. Money Market accounts sometimes have withdrawal limits (usually six per month) and may pay slightly higher APY in exchange.
Interest earned on certificates of deposit (CDs) versus savings accounts
CDs typically pay higher APY than savings accounts because you agree to lock your money away for a set term—three months, six months, one year, or five years. A one-year CD might pay 5.0% APY while a savings account pays 4.5%. The tradeoff: you can't touch the money without paying an early withdrawal penalty, usually equal to a few months of interest.
If you have money you won't need for a year, a CD locks in a may provide rate. If rates fall after you buy the CD, you're protected—you still earn the higher rate. If rates rise, you're stuck earning the lower rate unless you pay the penalty and move the money. Calculate whether the penalty cost is worth it before withdrawing early.
For money you might need within a year, a high-yield savings account is safer because you can withdraw anytime without penalty. For money you're certain you won't touch, a CD ladder (buying multiple CDs with different maturity dates) lets you earn higher rates while keeping some money accessible each month.
Frequently Asked Questions
Do I have to pay taxes on savings account interest?
Yes. Interest earned is taxable income. Banks send you a 1099-INT form if you earned $10 or more in interest during the year. You report this on your tax return. The tax rate depends on your income bracket. If you earn $500 in interest and you're in the 24% tax bracket, you owe roughly $120 in federal tax on that interest.
What's the difference between APY and APR on a savings account?
APY (annual percentage yield) includes compounding; APR (annual percentage rate) does not. Banks use APY for savings accounts because it shows the real amount you'll earn. APR is used for loans. Always compare APY when shopping for savings accounts.
Can a bank lower my interest rate without warning?
Yes. Banks can change APY anytime without notice. They usually notify you by email or statement, but they're not required to ask permission. If your rate drops significantly, you can move your money to another bank. There's no penalty for transferring savings between institutions.
Is my interest may provide if I open a CD?
Yes, the rate is locked in for the CD term. If you withdraw early, you pay a penalty, but the rate itself doesn't change. When the CD matures, the bank offers you a new rate, which may be higher or lower than what you earned before.
How often should I check my savings account interest rate?
Check every three to six months. Rates change frequently, and you might be earning significantly less than what's available elsewhere. If your rate has dropped more than 0.5% below the market rate, moving your money could earn you hundreds of dollars more per year.