APY vs. Interest Rate on Savings: What's the Difference?
Two savings accounts can advertise numbers that look close but aren’t actually comparable, simply because one is quoting a rate and the other is quoting a yield.
The short answer
The interest rate on a savings account is the base percentage used to calculate interest before compounding is factored in, while the APY, or annual percentage yield, reflects the total amount earned over a year including the effect of compounding. Because compounding means interest earns interest, the APY on an account is always equal to or higher than its stated interest rate, and APY is the more accurate figure for comparing what an account will actually pay over a year.
Why compounding creates the gap
Interest on a savings account is typically calculated and added to the balance on a regular schedule — daily, monthly, or quarterly, depending on the institution. Once that interest is added, the next round of interest is calculated on the new, slightly larger balance, which is what compound interest means in practice. The more frequently interest compounds, the bigger the gap between the simple interest rate and the resulting APY, since more frequent compounding gives interest more chances to earn on itself within the same year.
A simplified illustration
Imagine two accounts both advertise the same stated interest rate, but one compounds monthly and the other compounds daily. Run for a full year on an identical starting balance, the daily-compounding account will produce a very slightly higher total, because interest is being added to the balance more often and each addition starts earning its own interest sooner. The APY figure is designed to capture that difference by expressing the total yearly return as a single number, so the two accounts’ APYs would differ slightly even though their stated rates were identical — which is exactly the kind of gap that makes APY the more useful figure for comparison.
Why APY is the number to compare
Because APY already factors in compounding frequency, it allows an apples-to-apples comparison between accounts that compound on different schedules, which the plain interest rate doesn’t do on its own. This matters when comparing a high-yield savings account at one institution against a similar account elsewhere, and it applies just as much when weighing a savings account against a certificate of deposit, since a lower stated rate with more frequent compounding could end up producing a similar or higher APY than a higher stated rate compounding less often. Advertised APYs are also required to be presented consistently by regulation, which makes them a more reliable shorthand than the underlying rate for shopping around.
What APY doesn’t tell you
APY reflects the yield if the rate stays constant for a full year and no deposits or withdrawals are made, which isn’t always realistic. Many savings account rates are variable and can change at the bank’s discretion, meaning the APY quoted today isn’t a promise about what the account will pay in six months. It’s also specific to the account balance and terms current at the time it’s advertised, so it’s worth checking whether a quoted APY applies to the full balance or only to a portion of it, since some accounts use tiered rates that pay different APYs depending on the balance held.
What to weigh
When comparing savings options, the APY is generally the more useful number because it accounts for compounding and allows a fairer comparison across accounts with different schedules. But because rates set by banks and credit unions can change over time, it’s worth treating any advertised APY as a snapshot rather than a fixed promise, and periodically checking whether an account’s current APY still holds up against other options.