Annual Percentage Yield is the real rate your money grows each year

Annual Percentage Yield (APY) is the percentage of your savings balance that a bank will pay you in interest over one year, accounting for compounding. If you deposit $1,000 in an account with 4.50% APY, you will earn roughly $45 in interest over twelve months—though the exact amount depends on how often the bank compounds that interest and whether your balance stays constant.

APY is different from the interest rate alone because it includes the effect of compounding. Compounding means the bank pays interest on your interest. If your account compounds daily, you earn a tiny bit of interest each day, and the next day you earn interest on that previous day's interest too. Over a year, this stacking effect adds up. A bank might advertise a 4.50% interest rate, but the APY could be slightly higher because of daily compounding.

Banks are required by federal law to show you the APY, not just the interest rate. This makes it easier to compare accounts across different banks, because you are looking at the same metric everywhere.

Key Takeaways

  • APY shows what percentage of your balance you will earn in interest over one year, including the effect of compounding.
  • The more often a bank compounds interest (daily versus monthly, for example), the higher your APY will be at the same stated interest rate.
  • Banks must display APY on savings accounts so you can compare rates fairly across institutions.
  • Your actual earnings depend on your balance staying the same; withdrawals or deposits during the year will change the total interest you receive.

How compounding changes what you actually earn

Compounding frequency matters because it determines how many times per year the bank calculates and adds interest to your account. Most savings accounts compound interest daily. Some older or smaller accounts compound monthly or quarterly.

Here is a concrete example. Suppose you have $10,000 in an account with a 4.00% interest rate. If the bank compounds daily, it divides 4.00% by 365 days and calculates interest each day on your current balance. After day one, you have $10,000 plus one day's worth of interest. On day two, the bank calculates interest on that slightly larger amount. By the end of the year, daily compounding produces an APY of about 4.08%—higher than the stated 4.00% rate.

If that same account compounded monthly instead, the APY would be about 4.07%. If it compounded quarterly, about 4.06%. The difference sounds small, but on a $10,000 balance it means earning roughly $8 more per year with daily compounding than with quarterly compounding. On larger balances or over many years, the difference grows.

Where to find the APY and what it tells you

Banks display APY in the account disclosure documents they give you before you open an account. You will see it labeled as "APY" or "Annual Percentage Yield" on the account summary page of your bank's website, in the account agreement, or on printed materials in the branch.

The APY listed is the rate the bank is currently offering. Banks change APY frequently—sometimes weekly—based on what the Federal Reserve does with interest rates. A savings account that paid 4.50% APY last month might pay 4.25% this month. When you open an account, you lock in the APY that exists on that day, but the bank can lower it at any time with notice (usually 30 days).

The APY assumes your balance stays the same for the entire year. If you deposit money partway through the year or withdraw money, your actual interest earnings will be lower, because you did not have the full balance earning interest for the full twelve months.

APY versus interest rate: why the difference matters

The interest rate is the percentage the bank pays on your balance. The APY is that rate plus the effect of compounding. Banks can legally advertise either one, but federal law requires them to show you the APY so you can compare fairly.

A bank might advertise "4.00% interest rate" but the APY is "4.08%"—the difference is compounding. When you see two banks side by side, always compare their APYs, not their interest rates. A bank advertising 4.10% APY is paying you more than a bank advertising 4.00% APY, even if the second bank mentions a higher interest rate somewhere in the fine print.

How your balance affects total interest earned

APY tells you the percentage, but your actual dollar earnings depend on how much money sits in the account. A $1,000 balance earning 4.50% APY generates about $45 in interest over a year. A $10,000 balance at the same 4.50% APY generates about $450.

Your balance also has to stay relatively stable for the APY calculation to hold true. If you deposit $5,000 on day one and withdraw it on day 180, you earned interest on that $5,000 for only half the year, so your total interest is roughly half of what the APY would suggest. Banks calculate interest based on your daily balance, so every deposit and withdrawal changes the amount you earn.

Why banks offer different APYs

Banks set APY based on what the Federal Reserve charges them to borrow money and what they can earn by lending that money out. When the Fed raises rates, banks eventually raise savings APYs to compete for deposits. When the Fed lowers rates, savings APYs fall.

Different types of accounts also earn different APYs. A money market account might pay more than a regular savings account. A certificate of deposit (CD) might pay more than either, because you agree to lock your money away for a set time. Online banks typically offer higher APYs than brick-and-mortar banks because they have lower operating costs.

What happens to APY when interest rates change

The APY your bank advertises today is not may provide to stay the same. Banks can lower APY on savings accounts at any time, though they must notify you first—usually 30 days in advance. Some banks lower APY within weeks of opening an account if the Fed cuts rates.

If you want to lock in a rate, a certificate of deposit (CD) is the tool for that. A CD's APY is fixed for the entire term—three months, one year, five years, whatever you choose. A regular savings account APY can change whenever the bank decides.

Frequently Asked Questions

Does APY change if I withdraw money during the year?

The APY itself does not change, but your actual interest earnings will be lower. APY is an annual rate; if you withdraw money partway through the year, you earned interest on a smaller balance for part of that time. Banks calculate interest daily based on your actual balance, so every withdrawal reduces what you earn.

Is APY the same as interest rate?

No. Interest rate is the percentage the bank pays on your balance. APY includes the effect of compounding—earning interest on your interest. At the same interest rate, daily compounding produces a higher APY than monthly compounding. Banks must show you the APY so you can compare accounts fairly.

Can a bank lower my APY after I open an account?

Yes. Banks can lower APY on savings accounts at any time with notice, usually 30 days. If you want a may provide rate, open a certificate of deposit (CD), which locks in the APY for the entire term. Savings accounts have variable APY that changes with market conditions.

How often does the bank add interest to my account?

Banks calculate interest daily but add it to your account monthly or quarterly, depending on the account. The APY accounts for daily calculation, so you earn interest on your interest even if the bank does not physically deposit it until month-end. Check your account agreement to see when interest posts.

What APY should I look for in a savings account?

That depends on current market conditions and what banks are offering. Online banks typically offer higher APYs than traditional banks. Compare APYs across several banks before opening an account. Remember that a higher APY today may be lower next month if the Fed cuts rates, so lock in a CD if you want to may provide a rate.