The interest you earn depends on the bank's rate and how much money you keep there

A savings account earns interest, which is money the bank pays you for letting them use your deposit. The amount you earn is not fixed — it changes based on two things: the annual percentage yield (APY) the bank offers, and the balance you keep in the account.

Here is the simplest version: if you have $1,000 in an account with a 4.5% APY, you earn roughly $45 per year. If you have $10,000 at the same rate, you earn roughly $450 per year. The bank calculates this daily or monthly, depending on the account, and deposits the interest into your account automatically.

The catch is that APY rates vary widely between banks and change over time. A savings account at a large national bank might offer 0.01% APY, while an online bank might offer 4.5% or higher. The difference between these two is enormous — on $10,000, you would earn $1 per year at the first bank and $450 per year at the second.

Key Takeaways

  • Interest earned = your account balance × the APY rate ÷ 12 (for monthly), though banks calculate it daily and compound it automatically.
  • APY rates vary from under 0.01% at large national banks to 4% or higher at online banks and credit unions, so the bank you choose matters more than the balance.
  • Interest compounds, meaning you earn interest on your interest, but the effect is small in savings accounts unless you leave money untouched for years.
  • Your interest 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.

How banks calculate the interest you earn

Banks use a formula: your balance multiplied by the APY, divided by the number of days in a year. They do this calculation every single day, then add up all those daily amounts and deposit the total into your account monthly or quarterly.

For example, if you have $5,000 in an account with 4.5% APY, the bank calculates: $5,000 × 0.045 ÷ 365 = $0.62 per day. Over 30 days, that is roughly $18.60. Over a full year without touching the balance, it is roughly $225.

The reason banks calculate daily instead of once a year is compounding — interest earns interest. When the bank deposits your monthly interest into the account, that interest becomes part of your balance. The next month, you earn interest on the original balance plus the interest from the previous month. Over time, this compounds and grows faster than straightforward math would suggest. However, in a savings account, the effect is small unless you leave the money untouched for many years.

Why the APY rate matters far more than your balance

The bank you choose determines your rate, and rates vary dramatically. A person with $50,000 at a bank offering 0.01% APY earns $5 per year. A person with $5,000 at a bank offering 4.5% APY earns $225 per year. The second person earns 45 times more money on one-tenth the balance.

Rates also change over time. When the Federal Reserve raises or lowers interest rates, banks adjust their APY within days or weeks. An account that paid 4.5% six months ago might pay 4.25% today. This is why checking your bank's current rate before opening an account matters — and why moving money to a higher-rate bank can be worth the effort if you have a large balance.

Online banks and credit unions typically offer higher rates than large national banks. This is because online banks have lower overhead costs and compete for deposits by offering better rates. Large national banks often prioritize other services and offer minimal interest to savings customers.

What happens to your interest at tax time

Interest you earn is taxable income. If you earned $10 or more in interest during the year, the bank sends you a Form 1099-INT in January. You report this amount on your tax return, and you owe income tax on it at your regular tax rate.

This means earning $225 in interest might cost you $50 to $75 in taxes, depending on your tax bracket. It is still money you did not have before, but it is less than the full amount. If you earned less than $10 in interest, the bank does not send a form, but you still owe tax on it if you file a return.

How to compare interest rates between banks

When you are choosing where to open a savings account, look at the APY, not the interest rate. APY includes the effect of compounding and is the true number that tells you what you will earn.

Write down the APY from each bank you are considering, then use a straightforward calculator: multiply your expected balance by the APY to see your annual earnings. A difference of 1% APY on $10,000 is $100 per year — small enough that convenience might matter more, but large enough to notice over time.

Keep in mind that some banks offer higher rates only on balances above a certain amount, or only for the first few months. Read the fine print to see whether the rate you see is the permanent rate or an introductory offer.

Interest in high-yield savings accounts versus regular savings accounts

A high-yield savings account is straightforward a savings account with a higher APY. There is no special trick — the bank just offers a better rate. These accounts are usually at online banks or credit unions, and they work exactly like regular savings accounts: you deposit money, earn interest, and can withdraw whenever you need it.

The tradeoff is that high-yield accounts sometimes have higher minimum balances, or they limit the number of withdrawals you can make per month. Some also require you to open a checking account at the same bank. Before opening one, check whether these restrictions matter to how you plan to use the account.

When interest compounds and why it matters less than you think

Compounding means your interest earns interest. If you earn $10 in interest one month, the next month you earn interest on your original balance plus that $10. Over decades, this creates exponential growth — the reason Albert Einstein supposedly called it the eighth wonder of the world.

In a savings account, though, the effect is modest. On $10,000 at 4.5% APY, the difference between straightforward interest (no compounding) and daily compounding is about $2 per year. It matters more in retirement accounts or investments held for 20+ years, but in a savings account you are checking regularly, the practical difference is small.

Frequently Asked Questions

How often does the bank deposit interest into my account?

Most banks deposit interest monthly or quarterly. Some deposit daily. Check your account agreement or ask your bank. The frequency does not change how much you earn in a year — only the APY matters for that — but monthly deposits mean you see the money sooner.

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

No. Banks calculate interest daily, so you earn interest on the money for the days it was in the account. If you withdraw on the 15th, you earn interest for 15 days. You do not lose the interest you already earned, though you earn less that month because your balance was lower.

Can I move my money to a higher-rate bank without losing interest?

Yes. The interest you earned at the old bank stays in your account until you withdraw it. When you move the money to a new bank, you keep all the interest. You will just start earning the new bank's rate going forward.

What if the bank's APY drops after I open the account?

The bank can lower the rate on new deposits or on existing balances, usually with notice. You are not locked into the rate you saw when you opened the account. If rates drop significantly, you can move your money to a bank with a higher rate.

Is the interest I earn the same as my APY?

No. APY is the rate the bank offers. Interest is the actual money you earn. If your APY is 4.5% and your balance is $1,000, your interest for the year is roughly $45. APY is the percentage; interest is the dollars.