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What is APY?
APY (Annual Percentage Yield) is the yearly return on savings INCLUDING the effect of compounding — the true rate you actually earn. Formula: APY = (1 + r/n)^n − 1. It is the legal standard for quoting savings accounts and CDs (US Truth in Savings Act, 1991). APY is always ≥ the nominal rate; more frequent compounding produces a higher APY.
The full answer
The formula
``` APY = (1 + r/n)^n − 1
Where: r = nominal annual rate (decimal: 5% = 0.05) n = compounding periods per year (12 = monthly, 365 = daily) ```
APY is the *effective* annual rate — it tells you what you actually earn after a year of compounding, which is why savings products are legally quoted in APY (US Truth in Savings Act, 1991; Regulation DD). It is the saving-side mirror of APR: APR ignores compounding, APY includes it.
Worked example — same nominal rate, different APY by frequency
A 5% nominal rate:
| Compounding | APY |
|---|---|
| Annually | 5.000% |
| Monthly | 5.116% |
| Daily | 5.127% |
Daily compounding on 5% nominal yields 5.13% APY. APY is always ≥ the nominal rate; the gap widens with frequency (and with the rate itself).
Why savings are quoted in APY (and loans in APR)
Institutions quote the number that looks most favorable to them. Savings accounts advertise APY because compounding makes it *higher* than the nominal rate. Credit cards quote APR because ignoring compounding makes it *lower* than the true effective cost. Same underlying math, opposite framing — which is exactly why comparing on consistent units matters.
APY vs nominal rate vs APR
- Nominal rate — base rate, no compounding, no fees
- APY — nominal + compounding (the *saving* standard; always ≥ nominal)
- APR — nominal + fees, no compounding (the *borrowing* standard)
Where APY shows up
| Product | Note |
|---|---|
| High-yield savings (HYSA) | Usually daily compounding; APY tracks the Fed rate |
| Certificates of deposit (CDs) | Fixed APY locked for the term |
| Money-market accounts | Variable APY |
| Bond/treasury yields | Quoted as yield, conceptually similar |
Worked: $10,000 at 4.5% APY for 10 years ≈ $15,530 (≈ ×1.045 each year). Modest versus equities historically, but APY is the right metric for cash you need safe and liquid (emergency funds, short-term goals).
This explains how the yield is calculated — it is not financial advice. For personalized guidance consult a fee-only fiduciary (NAPFA.org).
Cross-reference: see /pages/what-is/apr + /pages/what-is-the-difference-between/apr-vs-apy + /pages/what-is/compound-interest + /pages/what-is/dividend-yield.
Time ranges by condition
| Condition | Duration | Note |
|---|---|---|
| Formula | APY = (1 + r/n)^n − 1 | — |
| 5% nominal, daily compounding | 5.13% APY | — |
| 5% nominal, monthly compounding | 5.12% APY | — |
| APY vs nominal rule | APY ≥ nominal always (compounding adds) | — |
| Legal basis | US Truth in Savings Act (1991), Reg DD | — |
What changes the time
- Compounding frequency. Daily > monthly > annual APY for the same nominal rate (effect widens at higher rates)
- Nominal rate. The base input; APY rises with it and the compounding gap grows
- Fees. APY does NOT include account fees — a monthly maintenance fee can erase the yield on a small balance
- Rate environment. Variable APY (HYSA, money-market) tracks the Fed rate; fixed APY (CDs) locks for the term
Common questions
What is the difference between APY and interest rate?
The (nominal) interest rate is the base rate before compounding; APY is the effective rate after compounding. For a 5% nominal rate compounded daily, the APY is about 5.13%. APY is always greater than or equal to the nominal rate — the more frequent the compounding, the larger the gap. Savings are quoted in APY so you see what you actually earn.
Why is APY higher than the stated rate?
Because APY includes interest-on-interest. If a bank pays 5% nominal and compounds daily, each day's interest itself earns interest for the rest of the year, lifting the effective yield to ~5.13%. The formula APY = (1 + r/n)^n − 1 captures this. Annual compounding makes APY equal the nominal rate; any more frequent compounding makes APY higher.
Does higher compounding frequency matter much?
Less than marketing implies. On a 5% rate, annual compounding gives 5.00% APY and daily gives 5.13% — a 0.13-point difference. The gap is larger at higher rates but still modest. Compare accounts on APY (which already bakes in frequency) rather than chasing "compounded daily" as a feature.
My HYSA advertises 4.5% APY — what does that mean?
It means that after a year of compounding you effectively earn 4.5% on your balance — APY already includes the compounding, so $10,000 becomes about $10,450 in a year (≈ $15,530 over 10 years). Watch for account fees, which APY does not include and which can erode the yield on small balances. APY is the right metric for safe, liquid cash; it is not investment advice.
Sources
We cite primary research, expert practice, and authoritative reference. Higher-tier sources weighted heavier. See methodology.
- T1US CFPB — savings account APY explainer — Authoritative consumer definition of APY + Truth in Savings
- T1US Federal Reserve — Regulation DD (Truth in Savings) — Legal basis for APY calculation + disclosure
- T1US FDIC — Consumer resources on deposit accounts — Government education on APY, CDs, compounding frequency
- T1Aswath Damodaran, NYU Stern — Effective annual rate mechanics
Cite this page
de Vries, P. (2026). What is APY?. AskedWell. Retrieved 2026-05-29, from https://askedwell.com/pages/what-is/apy
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