APY, or annual percentage yield, is the total amount of interest you earn on a deposit account over one year, including the effect of compound interest. It’s the single number that tells you what your savings will actually earn, not just the base interest rate. If you’re comparing savings accounts, money market accounts, or CDs, APY is the figure that matters most.
How APY Works
APY builds on a simple concept: when a bank pays you interest, that interest gets added to your balance. The next time interest is calculated, it’s based on the new, larger balance. This is compounding, and APY captures its full effect over a year.
Say you deposit $100 into an account with a 5% interest rate that compounds quarterly. At the end of the year, you’d have $105.09, not just $105. That extra nine cents comes from earning interest on interest. The APY in this case is 5.095%, which reflects what you actually earned, while the base rate (sometimes called the nominal rate) is just 5%. The gap between the stated rate and the APY grows wider as the interest rate or compounding frequency increases.
Two accounts can advertise the same interest rate but produce different earnings depending on how often they compound. An account paying 6% compounded monthly has an APY of 6.17%, while an account paying 6% with no compounding yields exactly 6%. Over larger balances and longer time periods, that difference adds up to real money.
Why Compounding Frequency Matters
Banks compound interest on different schedules: daily, monthly, quarterly, or annually. The more frequently interest compounds, the higher your APY. Daily compounding edges out monthly, which beats quarterly, and so on. Most high-yield savings accounts compound daily, which is one reason their advertised APY tends to be slightly higher than the underlying rate.
Every time interest compounds, the new interest payment gets folded into your principal. Future interest is then calculated on that larger number. Over a single year on a modest balance, the difference between daily and monthly compounding might only be a few cents. But on a $50,000 balance at 4% APY, you’re earning roughly $2,000 a year, and compounding frequency can shift that by $10 to $20 depending on the schedule. The APY number already accounts for this, so when you compare two accounts by APY alone, you’re making an apples-to-apples comparison regardless of how each bank structures its compounding.
APY vs. APR
APY measures what you earn on deposits. APR (annual percentage rate) measures what you pay on borrowed money, like loans or credit cards. They’re related concepts but used in opposite directions. Banks advertise APY on savings products and APR on lending products. Federal law requires both disclosures: the Truth in Lending Act mandates that lenders show you the APR, and a parallel rule requires banks to disclose the APY on deposit accounts so you can shop around.
APR includes certain fees but does not factor in compounding. APY does factor in compounding. This distinction matters because it means a loan’s true cost can be slightly higher than the stated APR if interest compounds, while a savings account’s APY already gives you the complete picture. When you’re saving, look for the highest APY. When you’re borrowing, look for the lowest APR.
Where You’ll See APY
APY shows up on savings accounts, high-yield savings accounts, money market accounts, checking accounts that pay interest, and certificates of deposit. As of early 2026, the national average savings account APY sits around 0.59%, while the top high-yield savings accounts offer rates between roughly 3.80% and 4.21%. That’s a seven-fold difference, which on a $10,000 balance translates to about $59 versus $420 in annual interest. Shopping around is worth the effort.
Fixed APY vs. Variable APY
Not all APY rates stay the same after you open an account. The distinction between fixed and variable APY determines whether your earnings are locked in or subject to change.
CDs typically offer a fixed APY. Once you open a CD, the rate holds steady for the entire term, whether that’s six months or five years. You know exactly what you’ll earn, but your money is locked up until the CD matures (with an early withdrawal penalty if you pull it out sooner).
Savings accounts, money market accounts, and interest-bearing checking accounts almost always carry a variable APY. The bank can adjust the rate in response to broader economic conditions, particularly changes to the federal funds rate set by the Federal Reserve. When the Fed raises rates, variable APYs tend to climb. When rates fall, your yield drops too. Banks are required to give you 30 days’ notice before reducing your APY, but they have no obligation to keep it at the level that attracted you in the first place. If you opened a high-yield savings account at 5% last year and rates have since fallen, your current APY could be meaningfully lower.
Calculating APY Yourself
The formula is straightforward if you want to check a bank’s math. APY equals (1 + r/n) raised to the power of n, minus 1. In that formula, “r” is the annual interest rate expressed as a decimal, and “n” is the number of times interest compounds per year.
For a 5% rate compounding quarterly: (1 + 0.05/4) to the fourth power, minus 1, equals 0.05095, or 5.095% APY. For a 4% rate compounding daily: (1 + 0.04/365) to the 365th power, minus 1, equals about 4.08% APY. You won’t need to do this math often since banks are required to display the APY, but it’s useful if you want to compare a rate quote that only lists the nominal interest rate and compounding schedule.
Taxes on Interest Earnings
Interest you earn in a standard savings account, CD, or money market account is taxable as ordinary income. If a bank pays you $10 or more in interest during the year, it will send you a 1099-INT form reporting that amount to both you and the IRS. Even if you earn less than $10, you’re still required to report the interest on your tax return. The form just won’t be issued automatically below that threshold.
This means your effective return after taxes is lower than the advertised APY. If you’re in the 22% federal tax bracket and earn $400 in interest, you’ll owe $88 in federal income tax on that amount, bringing your net earnings to $312. State income taxes may apply as well, depending on where you live. Interest earned inside tax-advantaged accounts like IRAs is not taxed in the year it’s earned, which can make those accounts more efficient for long-term savings.
Getting the Most From APY
The simplest way to maximize your interest earnings is to keep your savings in the highest-APY account you can find with terms that work for your situation. Online banks consistently offer higher APYs than traditional brick-and-mortar banks because they have lower overhead costs. The gap between a typical national bank savings account at 0.59% APY and a top online savings account above 4% is substantial.
If you don’t need access to your money for a set period, a CD can lock in a fixed APY that won’t drop if rates fall. If you want flexibility to deposit and withdraw freely, a high-yield savings account with a variable APY is the better fit. Either way, look at the APY rather than just the interest rate, confirm how often interest compounds, and check whether any minimum balance requirements or fees could eat into your earnings. A 4% APY doesn’t help much if the account charges a $15 monthly fee that wipes out your interest on a small balance.