APR vs APY: The One-Letter Difference That Hides Real Money

APR (annual percentage rate) and APY (annual percentage yield) are reported on virtually every loan, deposit account, and credit card you touch. They're not interchangeable — and which one you're looking at depends on whether the institution wants the number to look bigger or smaller.

The core distinction

APR is the interest rate without compounding factored in. APY is the interest rate with compounding factored in. For a single year, with no compounding (or annual-only compounding), APR and APY are identical. For monthly or daily compounding, APY is always slightly higher than APR.

The math

For a nominal rate r compounded n times per year:

APY = (1 + r/n)ⁿ − 1

At 5% APR compounded monthly: APY = (1 + 0.05/12)¹² − 1 = 5.116%. The difference looks small, but on a $50,000 deposit over 30 years, the APY-vs-APR distinction is the difference between $216,097 and $221,667 — about $5,500.

The compounding-frequency effect

• 5% APR compounded annually → 5.000% APY
• 5% APR compounded quarterly → 5.094% APY
• 5% APR compounded monthly → 5.116% APY
• 5% APR compounded daily → 5.127% APY
• 5% APR compounded continuously → 5.127% APY (limit)

Beyond daily, compounding frequency stops mattering — the marginal benefit collapses to nothing. So when a bank brags "we compound continuously," it's essentially marketing on a number that's identical to "compounded daily."

How institutions exploit the framing

Lenders quote APR because it makes the cost of borrowing look smaller. Banks quote APY on deposits because it makes the return look larger. Same underlying mechanic, opposite spin.

On a credit card with a 22.99% APR, the actual effective annual cost — if you carry a balance and let it compound monthly — is closer to 25.59% APY. That extra 2.6 percentage points is what your statement never explicitly shows you.

Loan APR includes more than just interest

For closed-end loans (mortgage, auto), APR is required by federal law (TILA) to reflect all required loan costs, not just the interest rate. So a 6.5% mortgage with origination fees and points might be quoted as "6.50% rate, 6.78% APR." The APR is more honest about total cost over the life of the loan.

This makes APR comparison-shopping useful: a low rate with high fees and a higher rate with no fees can both come out to the same APR, exposing the gimmick.

Practical reading guide

1. Savings & CDs: compare APY to APY. Two banks both quoting "5%" may have different compounding frequencies — APY normalizes them.
2. Credit cards: use APR as quoted, but mentally bump it up ~2 percentage points if you carry a balance.
3. Mortgages & auto loans: compare APR to APR (it includes fees) — but then double-check by running both quotes through a payment calculator. APR can mask differences if loan terms differ.
4. Promotional 0% APR offers: read the fine print for "deferred interest" — some retailers charge back-dated interest from the original purchase date if you don't pay off the entire balance by the promo end.

The mental model

APR is "what the rate is on paper." APY is "what the rate actually does to your money." When you're paying money, ask for APY (the bank won't volunteer it). When you're receiving money, the bank already gives you APY because it looks better.