Interest is calculated on your balance and paid monthly, but the exact amount depends on the rate your bank offers and how often they compound

Most banks calculate savings account interest daily but pay it to your account once a month. The bank takes your account balance, multiplies it by the annual interest rate, divides by 365 days, and repeats that calculation for each day of the month. At the end of the month, they add up all those daily amounts and deposit the total as interest into your account.

The rate itself varies by bank and by the type of savings account you hold. A standard savings account at a large national bank might pay 0.01% annually, while a high-yield savings account at an online bank might pay 4.5% or higher. The difference between these rates is real money: on a $10,000 balance, 0.01% earns $1 per year, while 4.5% earns $450 per year.

The timing matters too. Some banks use the average daily balance method, which adds up your balance each day and divides by the number of days in the month. Others use the ending balance method, which only looks at what you have on the last day of the month. A few use the lowest balance method, which counts only your smallest balance during the month. Most banks use average daily balance, but you should check your account agreement to know which one yours uses.

Key Takeaways

  • Banks calculate interest daily by multiplying your balance by the annual rate and dividing by 365, then deposit the total once a month.
  • The annual percentage yield (APY) printed on your account is the rate you will actually earn after compounding, so compare APY between banks, not the base rate.
  • Average daily balance is the most common calculation method, but some banks use ending balance or lowest balance instead — check your account agreement.
  • Moving money to a high-yield savings account can earn you 100 to 400 times more interest than a standard account at the same bank.

The difference between APR and APY

Banks list two different rates: the annual percentage rate (APR) and the annual percentage yield (APY). The APR is the base rate before compounding. The APY is what you actually earn after the bank adds interest back into your account and you earn interest on that interest.

For savings accounts, the difference is usually small because interest compounds monthly, not daily. But on larger balances or higher rates, it adds up. A bank might advertise 4.5% APR, but the actual APY could be 4.59% because you earn interest on the interest paid each month. Always compare the APY between banks, not the APR, because APY shows the real return you will receive.

How compounding works in your favor

Compounding means you earn interest on your interest. In month one, the bank pays you interest on your starting balance. In month two, they pay interest on your starting balance plus the interest from month one. Each month, the pool of money earning interest grows slightly larger.

The effect is small in the first few months but becomes visible over a year or longer. On a $10,000 balance at 4.5% APY, you earn about $37.50 in the first month. In month two, you earn interest on $10,037.50, not just $10,000. By the end of the year, you will have earned $450 instead of $450 divided by 12 months — the extra comes from compounding.

Some savings accounts compound daily instead of monthly, which means interest is calculated and added every single day. This earns you slightly more than monthly compounding, but the difference is usually a few dollars per year on typical balances. The bigger factor is the base rate your bank offers.

Why your interest payment changes month to month

If your interest payment looks different each month, it is usually because your balance changed. A larger balance earns more interest. A smaller balance earns less. If you deposited $5,000 in the middle of the month, that $5,000 only earned interest for half the month, so the interest payment that month will be lower than the next month when the full balance earns interest for the entire month.

Interest rates also change. Banks raise or lower their rates based on what the Federal Reserve does. If your bank raises the rate, your next month's interest payment will be higher. If they lower it, your payment will be lower. Banks must notify you before they lower a rate, but they can raise rates without notice.

The number of days in the month also affects the calculation slightly. February has fewer days than March, so your interest payment in February will be a bit lower than in March, even if your balance and rate stay the same.

How to find your account's interest rate and calculation method

Your bank's website usually shows the current APY for each account type. Log into your account and look for a rates page or account details section. You can also call the bank's customer service line and ask for the APY on your specific account type.

The account agreement or disclosure document explains how the bank calculates interest. You can find this in the paperwork you received when you opened the account, or request it from the bank. Look for sections titled "Interest Calculation," "How Interest Is Earned," or "Compounding." This document also tells you whether the bank uses average daily balance, ending balance, or lowest balance.

Your monthly statement shows the interest you earned that month. It usually lists the rate used and sometimes shows the calculation. If the amount seems wrong, you can use the rate and balance to verify it yourself, or contact the bank to ask them to explain the calculation.

Comparing interest rates across banks

The difference between a 0.01% account and a 4.5% account is enormous. On $50,000, the low-rate account earns $5 per year, while the high-rate account earns $2,250 per year. That is $2,245 in difference for doing nothing except moving your money.

Online banks and credit unions typically offer higher rates than large national banks. Online banks have lower overhead costs, so they pass some of that savings to customers through higher rates. Credit unions are member-owned, so they also tend to offer better rates. However, online banks may have fewer physical branches or ATMs, and credit unions require membership.

Rate comparison websites show current rates across many banks, but rates change frequently — sometimes weekly. Check the rate a few days before you move money to make sure it has not dropped. Also confirm that the bank is insured by the Federal Deposit Insurance Corporation (FDIC) or the National Credit Union Administration (NCUA), which protects your money up to $250,000 if the bank fails.

What happens if you withdraw money before the end of the month

You can withdraw money from a savings account at any time without penalty. The interest you earn is based on how long your money stays in the account during the month. If you withdraw $5,000 on the 15th of the month, that $5,000 only earns interest for 15 days, not the full month.

The bank calculates this using the average daily balance method. If you had $10,000 for the first 15 days and $5,000 for the remaining 15 days, your average daily balance is $7,500. Interest is calculated on that $7,500, not on the full $10,000. You do not lose any interest you already earned — you just earn less on the money that was withdrawn.

Frequently Asked Questions

Does interest compound daily or monthly?

Most banks compound monthly, meaning interest is calculated and added to your account once a month. Some high-yield accounts compound daily, which earns you slightly more. Check your account agreement or call your bank to find out which method yours uses. The difference is usually small — a few dollars per year on typical balances.

Why is my interest payment so small?

Interest rates are currently low at many banks. A standard savings account earning 0.01% on a $5,000 balance earns about 4 cents per month. High-yield accounts earn much more — the same $5,000 at 4.5% earns about $18.75 per month. Moving your money to a higher-rate account can make a real difference.

Can a bank change my interest rate without telling me?

Banks can raise rates without notice, but they must notify you before lowering a rate. You will receive notice by mail, email, or through your online account. If your bank lowers the rate and you do not like the new amount, you can move your money to another bank that offers a better rate.

What if I add money to my account mid-month?

The new money earns interest starting the day it is deposited. If you deposit $2,000 on the 20th of a 30-day month, that $2,000 earns interest for 11 days. The bank calculates this using average daily balance, so the new deposit increases your average balance for the rest of the month.

Is the interest I earn taxable?

Yes, interest earned on a savings account is taxable income. Your bank will send you a Form 1099-INT at the end of the year if you earned $10 or more in interest. You report this amount on your tax return. The amount is usually small, but it still counts as income.