The interest you earn depends on the account's APY, how much you deposit, and how long the money sits there

The dollar amount you earn is not fixed. A savings account earning 4.5% APY will pay you different amounts depending on your balance and how many days the money stays in the account. Banks calculate interest daily or monthly, then add it to your balance. The larger your balance and the longer it stays, the more you earn—but the rate itself is what changes most between accounts.

For example: $10,000 in an account with 4.5% APY earns roughly $450 per year if the balance stays constant. The same $10,000 in an account with 0.01% APY earns about $1 per year. That difference matters, especially if you are comparing savings accounts or deciding where to move money you plan to keep for months or years.

The catch is that most banks compound interest daily or monthly, meaning you earn interest on the interest you already earned. This compounds your growth slightly, but the effect is small on savings account balances. The real lever is the APY itself—which varies widely between banks and changes over time as the Federal Reserve adjusts rates.

Key Takeaways

  • Your earnings equal your balance multiplied by the APY, divided by 365 days (or 360, depending on the bank's method), then multiplied by the number of days your money is in the account.
  • A $50,000 balance at 4.5% APY earns roughly $2,250 per year; at 0.5% APY it earns roughly $250 per year—the same money, vastly different returns.
  • Interest compounds daily or monthly at most banks, so you earn small amounts of interest on your interest, but this effect is minor on savings balances.
  • Banks change their APY rates frequently, especially when the Federal Reserve raises or lowers its benchmark rate, so the amount you earn can shift month to month.
  • Online banks typically offer higher APY rates than brick-and-mortar banks because they have lower overhead costs.

How banks calculate the dollars you earn

Banks use a formula: Balance × APY ÷ 365 × Number of Days = Interest Earned. This is simplified—some banks use 360 days instead of 365, and some calculate daily while others calculate monthly—but the principle is the same. The interest is then added to your account, usually on a monthly statement date.

Here is a concrete example. You have $25,000 in a savings account with 4.0% APY. Over one year, you earn $25,000 × 0.04 = $1,000. If you leave the money for six months instead, you earn roughly $500. If you deposit $25,000 on January 15 and withdraw it on March 15 (59 days), you earn approximately $25,000 × 0.04 ÷ 365 × 59 = $161.64.

The timing matters because interest accrues only on days the money is actually in the account. Some banks credit interest on the first of the month; others credit it on the statement closing date. Check your account terms to see when your bank credits interest, because that affects when you can spend the earnings.

Why the same balance earns different amounts at different banks

The APY is the only number that changes the equation. Two banks holding your $50,000 will pay you vastly different amounts if one offers 4.5% APY and the other offers 0.5% APY. Over one year, that is a difference of $2,000 in your pocket.

Online banks (like Marcus, Ally, or Wealthfront) typically offer higher APY rates than traditional banks because they do not maintain physical branches or the staff to run them. They pass those savings to customers in the form of higher rates. A regional bank or credit union may offer competitive rates too, but you have to check—rates vary by institution and change frequently.

The Federal Reserve's benchmark rate is the main driver of APY changes across the industry. When the Fed raises rates, banks raise their savings APY within weeks or months. When the Fed cuts rates, banks cut their savings APY just as quickly. This is why the amount you earn can shift significantly from one year to the next, even if you do nothing.

How compounding affects your earnings

Most banks compound interest daily, meaning they calculate interest on your balance plus any interest you have already earned. Monthly compounding is less common but still happens at some institutions. The difference between daily and monthly compounding is small on savings balances, but it adds up over years.

Example: $100,000 at 4.5% APY with daily compounding earns roughly $4,591 in the first year (not exactly $4,500) because of the compounding effect. With monthly compounding, you earn roughly $4,585. The difference is $6—meaningful only if you are thinking in terms of decades. The real compounding power comes from leaving the money untouched for many years, which is rare with savings accounts people use for emergencies or near-term goals.

For most people, the APY rate matters far more than the compounding method. Switching from a 0.5% account to a 4.5% account is a 9× increase in earnings; the difference between daily and monthly compounding is less than 1%.

What happens when interest rates change

Banks adjust their APY rates in response to Federal Reserve decisions, but they do not all move at the same time or by the same amount. Some banks raise rates within days of a Fed increase; others wait weeks. Some cut rates when ready when the Fed signals a cut; others hold steady longer.

This means your earnings can change without you doing anything. If you have $50,000 earning 4.5% APY and your bank drops the rate to 3.5% APY, your annual earnings drop from $2,250 to $1,750—a loss of $500 per year. You do not lose the money you already earned, but future earnings are lower.

If your bank cuts rates and you want to keep earning more, you can move your money to a bank offering a higher rate. There is no penalty for moving savings between banks (unlike CDs, which charge early withdrawal fees). This is why it pays to check rates every few months if you have a large balance sitting in savings.

Comparing earnings across different account types

Savings accounts, money market accounts, and certificates of deposit (CDs) all earn interest, but at different rates and under different rules. A savings account lets you withdraw money anytime with no penalty. A CD locks your money for a set term (three months, one year, five years) and pays a higher rate in exchange. A money market account is a hybrid—it earns interest like a savings account but may require a higher minimum balance.

For the same bank, a one-year CD typically pays more than a savings account. A $50,000 CD at 4.8% APY earns $2,400 per year, while the same bank's savings account at 4.2% APY earns $2,100. The trade-off is that you cannot touch the CD money without paying an early withdrawal penalty (usually three to six months of interest). If you need the money sooner, the savings account is the better choice despite the lower rate.

High-yield savings accounts (offered by online banks) often pay as much as or more than CDs at traditional banks, with no lock-in period. This is why many people move money from brick-and-mortar banks to online savings accounts—they earn more and keep full access to their funds.

Taxes on savings account interest

The interest you earn is taxable income. If you earn $1,000 in interest during a calendar year, you owe federal income tax on that $1,000 at your ordinary income tax rate. Your bank will send you a 1099-INT form in January showing how much interest you earned, and you report it on your tax return.

State and local taxes may also explore, depending on where you live. Some states do not tax interest income; others do. This means the real return on your savings is lower than the APY suggests, because you have to pay taxes on the earnings. If you earn $1,000 in interest and your tax rate is 24%, you owe $240 in taxes, leaving you with $760 in actual after-tax earnings.

This is one reason people keep emergency funds in savings accounts rather than investing them—the interest is modest, but it is may provide and liquid. The tax hit is real but usually small compared to the benefit of having money you can access when ready.

Frequently Asked Questions

How often do banks pay interest on savings accounts?

Most banks credit interest monthly, on a set date each month. Some credit it quarterly or annually. Check your account terms or your most recent statement to see when your bank credits interest. The interest accrues daily, but you do not see it in your balance until the bank credits it.

Can I lose money in a savings account?

No. Your principal (the money you deposit) is protected by FDIC insurance up to $250,000 per account per bank. You earn interest on top of that principal. The only way your balance goes down is if you withdraw money or if fees exceed your interest earnings, which is rare at online banks.

What is the difference between APY and interest rate?

APY (annual percentage yield) includes the effect of compounding; the interest rate does not. For savings accounts, APY is the number that matters because it shows you the actual return you will earn over one year. Banks are required to display APY prominently so you can compare accounts fairly.

Do I earn interest if I withdraw money partway through the month?

Yes, but only for the days the money was in the account. If you deposit $10,000 on the 1st and withdraw it on the 15th, you earn interest for 14 days, not the full month. The bank calculates this automatically using the daily balance method.

Why do online banks pay more interest than traditional banks?

Online banks have lower operating costs because they do not run physical branches or employ tellers. They pass those savings to customers by offering higher APY rates on savings accounts. Traditional banks have higher overhead, so they offer lower rates to offset their costs.