What determines how much interest you earn
The amount of interest you earn depends on three things: how much money you have in the account, what annual percentage yield (APY) the bank offers, and how long the money sits there. A bank with a 4.5% APY will pay you more than one offering 0.01% APY, even if you deposit the same amount. The difference between accounts at the same bank can be hundreds of dollars per year on a $10,000 balance.
Interest compounds, meaning you earn interest on the interest you already earned. How often it compounds—daily, monthly, or annually—changes how much you end up with. Daily compounding pays slightly more than monthly, which pays slightly more than annual. Most online banks compound daily, which is why they tend to pay more total interest than brick-and-mortar banks that compound monthly or quarterly.
The length of time your money stays in the account matters too. Leave $5,000 in a savings account for one year at 4.5% APY and you earn roughly $225. Leave it for five years and you earn roughly $1,200 total (not $1,125, because of compounding). The longer it sits, the more interest stacks on top of itself.
Key Takeaways
- Your interest earnings equal your balance multiplied by the APY, divided by the number of days in a year, then multiplied by the number of days your money was in the account—but banks calculate this automatically.
- Moving from a 0.01% APY account to a 4.5% APY account on a $10,000 balance changes your annual earnings from roughly $1 to roughly $450.
- Daily compounding means you earn interest on yesterday's interest, which adds up to slightly more money over time than monthly or annual compounding.
- Interest rates change, so a bank offering 4.5% today may offer 3.8% in six months if the Federal Reserve lowers rates.
How banks calculate your interest payment
Banks use a formula: your daily balance multiplied by the APY, divided by 365 (or 366 in a leap year), then multiplied by the number of days the money was in the account. Most banks do this calculation every single day and add the tiny daily interest to your balance. That new balance then earns interest the next day, which is compounding.
You do not have to do this math yourself. Your bank statement or online dashboard shows your interest earned for the month or year. If you want to estimate before you open an account, multiply your balance by the APY as a decimal. A $10,000 balance at 4.5% APY earns roughly $450 per year ($10,000 × 0.045 = $450). For a partial year, divide that by 12 and multiply by the number of months.
Some banks pay interest monthly, others quarterly, and a few still pay annually. When they pay does not change how much total interest you earn over a year—it only changes when you see the money in your account. Monthly payments let you reinvest the interest sooner, which compounds faster.
Why APY varies so much between banks
Online banks typically offer higher APY than traditional banks because they have lower overhead costs. They do not maintain physical branches, so they pass some of that savings to customers through higher rates. A brick-and-mortar bank might offer 0.05% APY while an online bank offers 4.5% APY on the exact same type of account.
Banks also set rates based on what the Federal Reserve does. When the Fed raises its benchmark rate, banks usually raise savings APY within weeks. When the Fed cuts rates, banks cut savings APY more slowly—sometimes taking months. This is why your rate today might be 4.5% but drop to 3.8% six months from now without any action on your part.
Competition matters too. When one major online bank raises its rate to attract customers, others follow within days. When competition slows, rates can drift downward even if the Fed has not moved. Checking rates across banks every few months helps you catch when your current bank has fallen behind.
How much interest you earn on different balances
| Balance | APY 0.5% | APY 2.0% | APY 4.5% |
|---|---|---|---|
| $1,000 | $5 | $20 | $45 |
| $5,000 | $25 | $100 | $225 |
| $10,000 | $50 | $200 | $450 |
| $25,000 | $125 | $500 | $1,125 |
| $50,000 | $250 | $1,000 | $2,250 |
These figures assume the money stays in the account for a full year with no deposits or withdrawals. If you add money partway through the year, that new deposit earns interest only for the remaining months. If you withdraw money, you lose interest on that amount for the rest of the year.
The table shows why the difference between banks matters. Moving $25,000 from a 0.5% account to a 4.5% account costs you nothing upfront but earns you an extra $1,000 per year. Over five years, that difference compounds to roughly $5,200 more in your pocket.
What happens to your interest if rates drop
When the Federal Reserve cuts rates, your bank will eventually cut the APY on your savings account. The timing varies—some banks move within a week, others wait a month or longer. Your existing balance does not lose money, but the interest you earn on it going forward drops. A $10,000 balance earning $450 per year at 4.5% APY will earn only $200 per year if the rate drops to 2.0%.
You cannot lock in a rate on a regular savings account the way you can with a certificate of deposit (CD). Savings accounts have variable rates that change at the bank's discretion. If you want to protect yourself against rate cuts, you can move money into a CD, which locks in the rate for a set term—usually three months to five years. The tradeoff is that you cannot withdraw the money without paying an early withdrawal penalty.
Checking your savings account APY every few months helps you spot when your bank has fallen behind the market. If your bank drops to 2.0% APY while competitors offer 4.0%, moving your money takes about 15 minutes and could earn you an extra $200 per year on a $10,000 balance.
Interest earned versus interest paid on debt
Interest you earn in a savings account works in your favor—the bank pays you. Interest you pay on a credit card or loan works against you—you pay the bank. The math is the same, but the direction is opposite. A credit card charging 18% APR costs you $1,800 per year on a $10,000 balance, while a savings account at 4.5% APY earns you $450 per year on the same amount.
This is why paying off high-interest debt usually makes more financial sense than keeping extra money in savings. The interest you save by paying off a credit card at 18% APR is worth far more than the interest you earn in a savings account at 4.5% APY. Once high-interest debt is gone, then building savings in a high-yield account becomes worthwhile.
Frequently Asked Questions
Do I have to pay taxes on interest I earn in a savings account?
Yes. Interest earned in a savings account is taxable income. Your bank will send you a 1099-INT form 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, but it reduces the real value of the interest you earned.
What is the difference between APY and APR?
APY includes compounding, so it shows the actual amount you earn over a year. APR does not include compounding and is used for loans and credit cards. On a savings account, APY is the number that matters because it reflects what you actually get paid.
Can I earn interest on money in a checking account?
Some checking accounts pay interest, but the rate is almost always much lower than savings accounts—often 0.01% or less. Most people keep their everyday spending money in checking and their savings in a separate high-yield savings account to earn more interest.
What happens to my interest if I withdraw money mid-month?
You earn interest only on the balance for the days it was in the account. If you have $5,000 for 20 days and then withdraw it, you earn interest on $5,000 for only 20 days, not the full month. Banks calculate this daily, so the exact amount depends on when you withdraw.
Is there a maximum amount of interest I can earn?
No. The more money you have in the account and the higher the APY, the more interest you earn. There is no cap on interest earnings in a regular savings account. The only limit is the FDIC insurance cap of $250,000 per account holder per bank, which protects your deposits but does not limit interest.