What determines how much interest your savings account earns

The amount of interest you earn depends on three things: the annual percentage yield (APY) your bank offers, how much money you have in the account, and how long it stays there. A bank with a 4.5% APY will pay you roughly 4.5% of your balance per year, but the exact amount changes based on how your bank compounds the interest — whether it adds earnings to your balance daily, monthly, or quarterly.

Banks set their own APY rates based on what the Federal Reserve charges them to borrow money. When the Fed raises its rates, banks eventually raise what they pay on savings. When the Fed cuts rates, banks cut what they pay you. This means the APY you see today may be different in three months, and it will definitely be different in a year.

The difference between banks is real and worth checking. One bank might offer 4.75% APY while another offers 1.2% APY on the same type of account. Over a year, on $10,000, that gap costs you roughly $360 in lost interest.

Key Takeaways

  • Your interest earnings equal your account balance multiplied by the APY, divided by 365 days, then multiplied by the number of days your money sat in the account.
  • Banks compound interest at different intervals — daily compounding earns slightly more than monthly, which earns more than quarterly.
  • APY rates change whenever the Federal Reserve adjusts its rates, so the rate you lock in today will not stay the same forever.
  • High-yield savings accounts at online banks typically pay 4% to 5% APY, while traditional brick-and-mortar banks often pay under 1%.

How to calculate interest on your specific balance

The basic formula is: Interest = Balance × APY ÷ 365 × Number of Days. If you have $5,000 in an account earning 4.5% APY and leave it untouched for one full year, you earn roughly $225 in interest. If you leave it for six months, you earn roughly $112.50.

Most banks compound interest daily, which means they calculate what you owe and add it to your balance every single day. This matters because once interest is added, the next day's calculation includes that interest, so you earn interest on your interest. The difference between daily and monthly compounding is small on most balances — on $5,000 at 4.5%, you earn about $1.50 more per year with daily compounding — but it adds up over time and across larger balances.

Your bank's website or account statement will show you the exact APY and compounding method. Some banks display an estimated interest earnings figure right in your account dashboard, which saves you the math.

Why different banks pay different rates

Online banks typically pay higher APY than traditional banks because they have lower overhead costs — no physical branches, fewer employees, cheaper real estate. They pass some of those savings to customers in the form of higher interest rates. A bank like Marcus or Ally might offer 4.5% APY while your local credit union offers 0.5%, even though both are equally safe because both are insured by the FDIC or NCUA.

Banks also adjust rates based on how much money they need to attract. When a bank is growing fast and needs deposits, it raises its APY to pull in more customers. When it has plenty of deposits, it can lower the rate. This is why you see APY rates change month to month, sometimes week to week.

Money market accounts and certificates of deposit (CDs) sometimes pay higher rates than regular savings accounts at the same bank, but they come with restrictions — money market accounts may limit how many withdrawals you can make per month, and CDs lock your money away for a set period (three months, one year, five years) and charge a penalty if you withdraw early.

How compounding frequency affects your earnings

Compounding is how often the bank adds interest to your balance. With daily compounding, the bank calculates interest and adds it to your account every day. With monthly compounding, it happens once a month. With quarterly compounding, it happens four times a year.

The difference is small on modest balances but grows with larger amounts and longer time periods. On $50,000 at 4.5% APY for one year, daily compounding earns you roughly $2,305, while quarterly compounding earns roughly $2,300. That $5 difference seems tiny, but it compounds — if you leave the money untouched for five years, the gap widens to roughly $30.

Most online banks compound daily, which is why they often advertise their APY prominently. Traditional banks are more likely to compound monthly or quarterly. When you are comparing banks, check both the APY and the compounding frequency — a bank advertising 4.4% APY with daily compounding beats one advertising 4.5% APY with quarterly compounding.

What happens to your interest when rates change

When the Federal Reserve raises or lowers its rates, banks adjust what they pay on savings accounts within days or weeks. If you are in a high-yield savings account earning 4.75% and the Fed cuts rates, your bank will likely cut your APY to 4.5% or lower. You do not have to do anything — the change happens automatically.

This is why the interest you earn is not locked in. Unlike a CD, where your rate is may provide for the full term, a savings account rate can change at any time. Banks must notify you before they lower your rate, but they can lower it without your permission. If you want to lock in a rate, you need a CD.

The flip side: when rates rise, your APY rises too. If you are in a high-yield savings account and the Fed raises rates, your bank will likely raise what it pays you within a few weeks. This is why it pays to shop around when rates are climbing — moving your money from a bank paying 3.5% to one paying 4.75% means you earn an extra $625 per year on a $50,000 balance.

Interest earned on money you add or withdraw during the year

Banks calculate interest based on your balance on each day of the month. If you deposit $10,000 on the first of the month and leave it there, you earn interest on the full $10,000 for the entire month. If you deposit $10,000 on the 15th, you earn interest on that $10,000 for only half the month.

Withdrawals work the same way. If you withdraw $5,000 on the 20th of the month, you stop earning interest on that $5,000 from that day forward. The bank calculates your daily balance and compounds interest based on what was actually in the account each day.

This is why keeping money in savings longer earns more interest, even if the APY stays the same. A dollar sitting in the account for 365 days earns more than a dollar sitting there for 180 days.

Frequently Asked Questions

How much interest will I earn on $10,000 in a year?

At 4.5% APY, you earn roughly $450 per year on $10,000. At 1% APY, you earn roughly $100. The exact amount depends on whether the bank compounds daily or monthly and whether you add or withdraw money during the year. Your bank's website usually shows an estimated earnings figure if you enter your balance.

Is the APY the same as the interest rate?

No. APY includes the effect of compounding, while the interest rate does not. A bank might advertise 4.4% APY and 4.36% interest rate on the same account. The APY is what you actually earn because it accounts for interest being added to your balance and then earning interest itself.

Can my bank lower my interest rate whenever it wants?

Yes, banks can lower APY on savings accounts at any time, though they must notify you first. Unlike CDs, where your rate is locked in for the full term, savings account rates float and change based on what the Federal Reserve does and what the bank needs.

Do I pay taxes on savings account interest?

Yes. Interest earned on savings accounts is taxable income. Your bank will send you a 1099-INT form at the end of the year if you earned $10 or more in interest, and you report that amount on your tax return. This is why the interest you actually keep after taxes is less than the interest you earn.

Which type of account earns the most interest?

High-yield savings accounts and CDs typically pay the most. High-yield savings accounts currently pay 4% to 5% APY and let you withdraw anytime. CDs often pay slightly more but lock your money away for a set period. Money market accounts fall in between and sometimes require a higher minimum balance.