What you earn depends on the APY, your balance, and how long the money sits there

The amount of interest you gain in a savings account is determined by three things: the annual percentage yield (APY) the bank offers, how much money you keep in the account, and how long it stays there. A bank paying 4.5% APY on $10,000 for one year will add $450 to your account. The same bank paying 0.01% APY on the same $10,000 will add only $1. The difference between accounts at different banks can be hundreds of dollars per year on the same deposit.

Interest compounds, meaning you earn interest on the interest already credited to your account. How often that happens—daily, monthly, or quarterly—affects your total gain. An account that compounds daily will earn slightly more than one that compounds monthly, even at the same APY. Most online banks compound daily, which is why they often pay higher rates than brick-and-mortar banks.

The APY you see advertised is not may provide forever. Banks change rates frequently, sometimes weekly. When the Federal Reserve raises or lowers its benchmark rate, banks adjust their savings rates within days or weeks. If you lock in 4.5% today, that rate may drop to 3.8% next month if the Fed changes course. Conversely, if rates are rising, your rate may increase too—but only if the bank chooses to raise it.

Key Takeaways

  • Interest earned equals the APY multiplied by your balance, divided by 365 days (for daily compounding), then multiplied by the number of days the money sits in the account.
  • A $10,000 balance at 4.5% APY earns roughly $450 per year; at 0.01% APY it earns roughly $1 per year.
  • Daily compounding means you earn interest on previously earned interest, adding a small but real boost compared to monthly or quarterly compounding.
  • APY rates change frequently and are not locked in—your rate can drop or rise depending on what the bank decides and what the Federal Reserve does.

How to calculate interest on your own balance

The basic formula is: (Balance × APY) ÷ 365 × Number of Days = Interest Earned. If you have $5,000 in an account paying 3.5% APY and leave it untouched for 90 days, the math is ($5,000 × 0.035) ÷ 365 × 90 = $43.15. This assumes daily compounding and that the rate stays the same for the full period.

Most banks show you the projected interest on their website before you open an account. You can also use their savings calculator, which accounts for daily compounding automatically. If you plan to add money regularly—say, $500 per month—the calculator will show you a more accurate total because each deposit starts earning interest from the day it arrives.

Keep in mind that this calculation is before taxes. Interest earned in a savings account is taxable income. The bank will send you a 1099-INT form at tax time if you earned $10 or more in interest during the year. You will owe federal income tax on that amount, and possibly state income tax depending on where you live.

Why rates vary so much between banks

Online banks typically pay 4% to 5% APY on savings accounts, while traditional banks often pay 0.01% to 0.05%. The difference is not because online banks are more generous—it is because they have lower overhead. They do not maintain physical branches, employ as many staff, or pay for building rent and utilities. Those savings get passed to customers as higher interest rates.

Banks also compete for deposits. When one online bank raises its rate to 4.75%, others often follow within days to keep customers from moving their money. This competition benefits you if you shop around. A rate difference of even 1% can mean $100 per year on a $10,000 balance.

Credit unions sometimes offer competitive rates too, though they vary widely. Some credit unions pay 4% or higher on savings accounts, while others pay less than 1%. Membership requirements and account minimums differ by institution, so you will need to check your local credit union's current rates.

What happens when rates drop

If you open a savings account at 4.5% APY and the Federal Reserve cuts rates, your bank will likely lower your APY within weeks. Banks are not required to notify you in advance, though many do send an email or letter. Your rate can drop to 3.8%, 2.5%, or lower depending on market conditions and the bank's strategy.

This is why it matters to check rates regularly. If your bank drops to 1.5% APY and another bank is offering 4%, moving your money takes about 15 minutes. You can open a new account online, request an external transfer from your old bank, and the funds usually arrive within 1 to 3 business days. You lose no interest during the transfer because interest accrues daily.

Some people move their money between banks multiple times per year to chase the highest rate. This is legal and costs you nothing, though it may create multiple accounts to track. Others prefer to stay put for simplicity, accepting a lower rate in exchange for not managing multiple accounts.

How much interest you need to make it worthwhile

Whether a savings account makes sense depends on your goals. If you are saving for an emergency fund or a purchase within the next year or two, a high-yield savings account at 4% to 5% APY is better than keeping cash in a checking account earning 0.01%. On $10,000, the difference is $400 to $500 per year.

If you are saving for retirement or a goal 10+ years away, a savings account earning 4% may not keep pace with inflation or stock market returns. Historically, stocks have returned 7% to 10% annually over long periods, though with more risk. A savings account is safe but may not grow your money as fast as you need.

For money you need to access quickly—within 3 to 6 months—a high-yield savings account is usually the best choice. Money market accounts and certificates of deposit (CDs) sometimes pay slightly higher rates, but they often require larger minimums or lock your money away for months or years.

Fees that reduce your interest earnings

Some banks charge monthly maintenance fees, overdraft fees, or fees for falling below a minimum balance. A $10 monthly fee on an account earning $40 per year in interest cuts your gain in half. Always check the fee schedule before opening an account.

Most online banks charge no monthly fees and have no minimum balance requirements. Traditional banks often do charge fees, which is another reason their net interest earnings are lower even when their stated APY is higher. A bank advertising 2% APY with a $15 monthly fee is actually paying you less than a bank offering 1.5% APY with no fees.

Frequently Asked Questions

How often does interest get added to my savings account?

Most banks compound and credit interest daily, meaning you earn interest on your balance every single day. The total is usually deposited into your account monthly. Some banks compound quarterly or annually, which means you earn slightly less because you do not earn interest on the interest as frequently.

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 holder per bank. Interest rates can drop, which means you earn less, but your balance will not go down unless you withdraw money or the bank fails—which is extremely rare for FDIC-insured banks.

Is interest from a savings account taxed?

Yes. Interest is taxable income at both federal and state levels (in most states). If you earn $10 or more in interest during a calendar year, the bank sends you a 1099-INT form for tax filing. You report this amount on your tax return and pay income tax on it at your regular tax rate.

What is the difference between APY and interest rate?

APY (annual percentage yield) includes the effect of compounding, while the interest rate does not. A bank might advertise a 4.5% interest rate that compounds daily, which equals a 4.6% APY. The APY is the number that matters because it shows what you actually earn.

Should I move my money if rates drop?

If your current bank drops below 2% APY and another bank offers 4%, moving your money makes sense. The transfer takes 1 to 3 business days and costs nothing. You only lose interest if you withdraw and hold cash—the transfer itself does not interrupt your interest accrual.