The amount depends on your balance, the APY your bank offers, and how long the money sits there

A savings account earns interest by paying you a percentage of your balance each year. That percentage is your Annual Percentage Yield (APY). The actual dollars you earn come from multiplying your balance by that rate, divided into monthly or daily payments depending on how your bank compounds interest.

If you have $10,000 in an account earning 4.5% APY, you earn roughly $450 per year—but not all at once. Most banks calculate interest daily and deposit it monthly, so you'd see about $37.50 added each month. The exact amount shifts slightly because interest compounds: once the bank adds that $37.50, next month's calculation includes it, so you earn a tiny bit of interest on the interest itself.

The catch is that APY rates vary widely. A brick-and-mortar bank might offer 0.01% APY on a regular savings account, while an online bank might offer 4.5% or higher on the same type of account. That difference means $10,000 earns $1 per year at the first bank and $450 at the second. Where you keep your money matters far more than how much you keep.

Key Takeaways

  • Interest earned equals your balance multiplied by the APY, divided by 12 if the bank pays monthly or by 365 if it pays daily.
  • Online banks typically offer higher APY rates than traditional banks because they have lower overhead costs.
  • Interest compounds, meaning you earn small returns on the interest already paid to you, but the effect is modest on most balances.
  • Your balance changes the math: doubling your savings roughly doubles your annual interest, assuming the APY stays the same.
  • APY rates change over time, so the interest you earn this year may differ from next year if your bank adjusts its rate.

How the calculation actually works

Banks use a formula to turn APY into the dollars that land in your account. The simplest version is: Interest = Balance × APY ÷ 12 (if paid monthly). A $5,000 balance at 4.5% APY earns $5,000 × 0.045 ÷ 12 = $18.75 per month.

Most banks compound interest daily, which means they calculate what you've earned each day and add it to your balance before calculating the next day's interest. This sounds complex but the real-world difference is small. On $5,000 at 4.5% APY, daily compounding earns you roughly $0.50 more per year than straightforward monthly calculation. It matters more on larger balances or higher rates, but it's never the main factor in how much you earn.

The bank's compounding frequency appears in the fine print of your account agreement, usually labeled "compounding period" or "frequency of compounding." Daily compounding is standard at most online banks. Some older accounts or specialty products compound monthly or quarterly, which reduces your earnings slightly.

Why APY rates differ so much between banks

The APY your bank offers reflects what it costs them to run the business and what they can earn by lending your money out. Online banks offer higher rates because they don't maintain physical branches, don't employ tellers, and don't pay for real estate. That lower cost structure means they can pass more of their lending profits back to you as interest.

Traditional banks with branches often offer much lower rates on savings accounts—sometimes under 0.1% APY—because they rely on deposits to fund their lending business at a smaller margin. They make money on the spread between what they pay you and what they charge borrowers, and they can afford a smaller spread because they have other revenue from branches and services.

Federal Reserve policy also affects all rates. When the Fed raises its benchmark interest rate, banks raise APY on savings accounts. When the Fed cuts rates, banks cut APY. This means the interest you earn can change several times per year, usually announced by your bank with a few days' notice.

What happens to interest over time

Interest compounds, so the longer money sits in your account, the more you earn on your earnings. On $10,000 at 4.5% APY, you earn $450 in year one. In year two, if the rate stays the same and you don't touch the money, you earn interest on $10,450, which is $470. The difference is small in the early years but grows over decades.

This effect accelerates if you add money regularly. If you deposit $500 per month into a savings account earning 4.5% APY, after one year you've deposited $6,000 and earned roughly $135 in interest (because each deposit earns for a shorter time). After five years, you've deposited $30,000 and earned roughly $4,200 in interest. The compounding effect becomes visible once you have both time and a growing balance.

However, inflation erodes the real value of what you earn. If your account earns 4.5% APY but inflation runs at 3%, your money is only growing 1.5% in real purchasing power. This is why savings accounts are meant for money you need to access soon, not long-term wealth building.

How to compare interest across different banks

The only number that matters for comparison is APY, not "interest rate" or "annual rate." APY includes the effect of compounding, so it's the true measure of what you'll earn. A bank advertising "4.5% interest rate compounded daily" is showing you the APY. A bank showing "4.48% APY" is showing you the same thing in a different format—the APY already accounts for daily compounding.

Look at APY on the bank's website or in the account disclosure document, usually labeled "Annual Percentage Yield" or "APY." Compare only accounts of the same type: a high-yield savings account at one bank against a high-yield savings account at another, not against a money market account or CD, which have different terms and purposes.

Check whether the rate is promotional or permanent. Some banks offer a higher APY for the first few months, then drop it. The disclosure will say "introductory rate" or "promotional rate" if this applies. After the promotional period ends, your rate drops to the standard rate, which is usually much lower. Factor in how long you plan to keep the money when deciding whether a promotional rate is worth switching banks.

The difference between savings accounts and other places to keep money

A high-yield savings account at an online bank typically earns 4% to 5% APY. A regular savings account at a traditional bank typically earns 0.01% to 0.1% APY. The difference in annual earnings on $10,000 is roughly $400 to $500 per year—real money that compounds over time.

A money market account works like a savings account but usually requires a higher minimum balance and may offer a slightly higher rate in exchange. A Certificate of Deposit (CD) locks your money away for a fixed term (three months to five years) and pays a higher rate because the bank knows it can use your money for that entire period. You cannot withdraw from a CD early without a penalty, so they are not for money you might need soon.

A regular checking account earns little to no interest, even at online banks. Checking accounts are designed for spending and bill payments, not for storing money long-term. If you have money sitting in a checking account earning 0.01% APY, moving it to a high-yield savings account at the same bank could earn you 50 to 100 times more interest on the same balance.

What reduces the interest you actually receive

Taxes reduce your interest earnings. The interest your bank pays you is taxable income, reported on a 1099-INT form at tax time. If you earn $450 in interest and you're in the 22% federal tax bracket, you owe roughly $99 in federal income tax on that interest. Some states also tax interest income. This means your real after-tax earnings are lower than the APY suggests.

Fees can also eat into interest. Some savings accounts charge monthly maintenance fees, overdraft fees, or fees for falling below a minimum balance. A $10 monthly fee on an account earning $37.50 per month in interest cuts your real earnings by 27%. Most online banks waive these fees, but some traditional banks still charge them. Read the fee schedule before opening an account.

Inflation is the silent reducer. If you earn 4.5% APY but inflation runs at 3%, your money is only growing 1.5% in real value. Over a decade, that difference compounds significantly. This is why savings accounts are best for short-term goals (one to five years), not for money you won't need for decades.

Frequently Asked Questions

How often does interest get added to my account?

Most banks calculate interest daily but deposit it monthly. Some deposit weekly or quarterly. Check your account agreement or call your bank to confirm the frequency. The more often interest is deposited, the sooner it starts earning interest itself, but the difference is usually less than a dollar per year on typical balances.

If I withdraw money mid-month, do I lose all the interest for that month?

No. Banks calculate interest daily based on your balance each day, so you earn interest on the money for the days you held it. If you have $10,000 for 20 days and $5,000 for 10 days, you earn interest on both amounts for their respective periods. The exact amount depends on your bank's calculation method, but you won't lose a full month's interest for an early withdrawal.

Can I predict exactly how much interest I'll earn next year?

Not precisely, because APY rates change. You can estimate based on the current rate, but banks adjust rates based on Federal Reserve policy, usually several times per year. If rates stay the same, your estimate will be close. If rates rise or fall, your actual earnings will differ. Check your bank's website for the current APY before making projections.

Is it worth switching banks to get a higher APY?

It depends on your balance and how long you plan to stay. If you have $50,000 and can move it from 0.1% APY to 4.5% APY, you gain roughly $2,200 per year. If you have $2,000, you gain roughly $88 per year. The switching process takes a few days and involves setting up a new account and transferring money, so it makes sense for larger balances or if you're opening a new account anyway.

What happens to my interest if the bank lowers its APY?

Your interest earnings drop when ready when the rate changes. The bank must notify you before lowering rates, usually with a few days' notice. Interest already earned and deposited to your account stays yours. Only future interest is calculated at the new, lower rate. If you want to lock in a higher rate, a CD lets you do that for a fixed term.