APR vs APY: What's the Difference and Why It Matters

The One-Sentence Difference

APR (Annual Percentage Rate) is the simple annual interest rate — it does not account for compounding. APY (Annual Percentage Yield) is the effective annual rate after compounding is factored in. APR is almost always used to describe what you pay (credit cards, mortgages, auto loans). APY is almost always used to describe what you earn (savings accounts, CDs, money market accounts).

Those two rules of thumb aren't accidents. Lenders quote you APR because it looks lower than the true cost of borrowing. Banks quote you APY because it looks higher than the underlying rate they actually credit. The marketing math runs in opposite directions, which is exactly why you need to understand both.

Why Compounding Creates the Gap

Interest doesn't usually accrue once a year. It accrues monthly, daily, or sometimes even continuously, and each time it accrues it gets added to your balance. The next round of interest is then calculated on a slightly larger number. Over a full year, that "interest on interest" effect makes the actual yield higher than the nominal rate.

Consider a savings account with a 5% nominal annual rate that compounds monthly. The bank credits you 5%/12 = 0.4167% every month. After 12 rounds of compounding, the actual annual return is:

That's 0.116 percentage points higher — small, but on a $100,000 balance it's $116 a year in extra returns the APY number captures and the APR number doesn't.

The Formula That Converts One Into the Other

The conversion is mechanical once you know the compounding frequency:

For a credit card with a 24% APR compounded daily, the real APY is (1 + 0.24/365)^365 − 1 = 27.11%. That's the rate that actually applies to your unpaid balance. The 24% APR on the statement is the number the lender is required to disclose — but the 27.11% APY is the number that determines what you actually owe.

When APR Is the Honest Number

For most amortized loans — mortgages, auto loans, personal loans — APR is more useful than APY because the loan balance falls every month as you pay down principal. The compounding effect doesn't run away the same way it does on a savings balance, because you're constantly reducing the principal interest is calculated on. The federal Truth in Lending Act requires lenders to disclose APR specifically because it's a fair apples-to-apples comparison number across loans with different fee structures.

Mortgage APR, importantly, also bundles in certain closing costs and lender fees. A loan with a low headline interest rate but high origination fees may have a higher APR than a loan with a slightly higher interest rate but no fees. Always compare APRs, not nominal interest rates, when shopping for a mortgage. The mortgage calculator on this site lets you punch in different APR scenarios and see total cost side by side.

When APY Is the Honest Number

For deposit accounts, APY is the meaningful number — and the federal Truth in Savings Act requires banks to disclose APY for exactly this reason. Two savings accounts can have identical APRs but different APYs if one compounds daily and the other compounds quarterly. The APY tells you what you'll actually earn after a year, given the bank's compounding schedule.

When comparing high-yield savings accounts or CDs, ignore the headline interest rate and look at the APY. The same logic applies to investments: a fund advertising "1% monthly return" sounds like 12% a year, but compounded monthly it's actually 12.68% APY. The reverse is also true — a quoted 12% APY only requires ~11.39% annualized monthly compounding underneath.

The Credit Card Trap

Credit cards advertise APR but charge what's effectively APY, because they compound daily on unpaid balances. A "19.99% APR" card actually charges close to 22.1% APY on revolving balances. This is the single biggest reason credit card debt grows faster than people expect.

Comparing Two Loans or Two Savings Accounts Correctly

The rule is simple: always compare in the same unit. Convert everything to APY when comparing what you'll earn, and compare APRs when shopping for loans (since federal rules force lenders to include fees in the APR). Never compare a quoted APR on Loan A with a quoted APY on Loan B — that's an unfair fight by definition.

If a lender only quotes a "monthly interest rate," multiply by 12 to get the APR, then run the conversion formula above to get the true APY. If a savings ad quotes a "daily interest rate," your APY is (1 + daily rate)^365 − 1.

The Numbers That Matter Most

If you remember nothing else: APR ignores compounding, APY includes it. Lenders show you APR because it looks lower. Banks show you APY because it looks higher. Both numbers exist for legitimate reasons, but they're not interchangeable. Knowing which one is being quoted, and which one matters for your specific decision, is the entire skill. Once you have that, every loan comparison and every savings comparison becomes straightforward — you just put both products in the same units and pick the better one.