Interest is calculated daily but paid monthly, and the amount depends on your balance and the bank's rate

Your bank calculates interest on the money in your savings account every single day, but it only deposits that interest into your account once a month. The amount you earn depends on two things: how much money you have in the account and what annual percentage yield (APY) your bank is currently offering. If your account has $10,000 and your bank offers 4.5% APY, you do not earn 4.5% of $10,000 in a month — you earn roughly one-twelfth of that amount, because interest is divided across twelve months.

The actual calculation happens in the background. Your bank takes your daily balance, multiplies it by the annual rate, divides by 365 days, and repeats this for each day of the month. At the end of the month, it adds up all those daily amounts and deposits the total as a single payment. If your balance changes during the month — because you deposit money or make a withdrawal — the interest calculation adjusts for those changes automatically.

Key Takeaways

  • Interest is calculated on your daily balance but deposited once per month, usually on the last day or the first day of the next month.
  • The amount you earn each month is roughly your annual rate divided by 12, applied to your average daily balance.
  • Deposits made early in the month earn interest for more days that month than deposits made near the end.
  • Once interest is deposited, it becomes part of your balance and earns interest itself the following month — this is called compounding.

How the daily calculation works

Banks use a method called daily compounding for most savings accounts. Each day, the bank looks at your account balance at the end of business that day. It then multiplies that balance by the annual rate, divides by 365, and that is your interest for that one day. The next day, it does the same thing with your new balance — which now includes the previous day's interest, even though you have not seen it yet.

Here is a concrete example. Suppose you have $5,000 in an account with 4% APY. On day one, the bank calculates: $5,000 × 0.04 ÷ 365 = $0.55 in interest for that day. On day two, if your balance is still $5,000, you earn another $0.55. But if you deposited $1,000 on day two, your new balance is $6,000, so day two's interest is $6,000 × 0.04 ÷ 365 = $0.66. The bank repeats this for all 30 or 31 days of the month, then adds up all the daily amounts and deposits the total.

The reason banks do this is that it rewards you for money that sits in the account longer. A dollar deposited on the first of the month earns interest for 30 days. A dollar deposited on the 15th earns interest for only 15 days. The daily method captures that difference automatically.

When interest actually shows up in your account

Interest deposits happen on a schedule set by your bank, usually the last business day of the month or the first business day of the next month. Some banks deposit on the 15th and the last day. You can find your bank's schedule in the account agreement or by calling customer service — it does not vary month to month, but different banks use different dates.

The interest is calculated through the last day of the month, even if the deposit does not hit your account until the first or second day of the next month. That timing matters if you are watching your balance closely or if you are about to withdraw money. If you withdraw $5,000 on the last day of the month, you will not earn interest on that $5,000 for that month, because the bank calculates based on the balance at the end of each day.

Once the interest deposits, it sits in your account as regular money. You can withdraw it, or you can leave it there. If you leave it there, it becomes part of your balance for the next month's calculation, and it earns interest itself.

How compounding increases what you earn over time

Compounding means earning interest on your interest. In month one, you earn interest on your original deposit. In month two, you earn interest on your original deposit plus the interest from month one. In month three, you earn interest on all three amounts. The longer money sits in the account, the more this effect adds up.

The difference is small in the short term but real over years. A $10,000 deposit at 4% APY earns roughly $40 in the first month. In month two, you earn interest on $10,040, not just $10,000 — a difference of $0.13. After one year, you have earned about $408 total, not $400. After five years, the compounding effect means you have earned roughly $2,190 instead of $2,000. The longer you leave the money untouched, the more compounding works in your favor.

Why your monthly interest amount changes

Your interest payment is not the same every month because your balance is not the same every month. If you deposit $2,000 in the middle of the month, your balance for the second half of the month is higher, so your interest for that month is higher. If you withdraw $3,000, your balance drops and so does your interest.

Your interest also changes when your bank changes its APY. Banks adjust rates based on what the Federal Reserve does with its benchmark rate. When the Fed raises rates, banks typically raise the APY they offer on savings accounts within days or weeks. When the Fed cuts rates, banks usually cut their APY as well. You will see the new rate reflected in your next month's interest payment.

The difference between APY and APR on savings accounts

APY (annual percentage yield) is what matters for savings accounts. It includes the effect of compounding — it shows you the actual percentage you will earn in a year if you do not touch the money. APR (annual percentage rate) does not include compounding and is rarely used for savings accounts. Banks are required to show you the APY in the account agreement and on the website, so that is the number to compare when you are shopping for accounts.

If a bank advertises 4.5% APY, that means if you deposit $10,000 and leave it for a full year without touching it, you will have roughly $10,450 at the end of the year. The actual amount varies slightly depending on how many days are in the month and how the bank counts, but APY gives you an accurate picture of what you will earn.

What happens if you withdraw money before the interest deposits

If you withdraw money on the 28th of a 30-day month, you lose interest on that money for the days you did not hold it. The bank calculates interest based on the balance at the end of each day, so once the money is gone, it stops earning. You will still receive interest on the money that remains in the account.

Some banks have minimum balance requirements, and if your balance falls below that minimum, they may charge a fee or lower your APY for the next month. Check your account agreement to see if yours does. If you are planning to withdraw a large amount, it is worth checking whether you will drop below the minimum and what the consequence is.

Frequently Asked Questions

Can I earn interest on interest that has not been deposited yet?

No. Interest is calculated daily, but it does not officially become part of your balance until the bank deposits it, usually at the end of the month. Until then, it is pending. Once it deposits, it becomes part of your balance and earns interest the next month.

Do I have to do anything to get the interest, or does it happen automatically?

It happens automatically. You do not have to take any action. As long as your account is open and active, the bank calculates and deposits interest on its schedule. You will see it appear in your account on the deposit date.

What if my bank changes the interest rate in the middle of the month?

The new rate applies to the remaining days of that month. If your bank raises the rate on the 15th, you earn the old rate for days 1–14 and the new rate for days 15–30. The interest for that month reflects both rates.

Does a savings account earn more interest if I add money regularly?

Yes. Each deposit increases your balance, so you earn interest on a larger amount. A deposit made early in the month earns interest for more days than a deposit made near the end. Regular deposits compound the effect over time.

How do I know what APY my bank is currently offering?

Log into your online account or call your bank's customer service line. The APY is also listed on your monthly statement and in the account agreement. Rates change frequently, so checking your statement each month shows you what you are currently earning.