When banks advertise savings accounts, CDs, and money-market accounts, the number that actually matters is the APY — Annual Percentage Yield. While the nominal APR (Annual Percentage Rate) is the raw interest rate before compounding, the APY reflects what you truly earn after compounding is applied. Because interest is calculated on a growing balance, a 5% APR compounded monthly earns 5.116% APY, while the same 5% compounded daily earns 5.127% APY. This APY calculator converts any nominal APR to its true APY and shows how the frequency of compounding changes your earnings — everything runs privately in your browser; nothing is uploaded or stored.
Compounding frequency is why two accounts advertising the same rate can pay differently. Monthly compounding means interest is added twelve times a year; daily compounding adds it 365 times. Each new interest payment starts earning its own interest immediately, so more frequent compounding always produces a slightly higher effective yield. The formula behind the conversion is APY = (1 + r/n)n − 1, where r is the nominal APR as a decimal and n is the number of compounding periods per year. For continuous compounding, the formula is APY = er − 1.
For comparing products, APY is the only number you need: it already bakes in compounding, so two accounts can be compared apples-to-apples regardless of how often they compound. A $10,000 deposit at 5.25% APY grows to $12,903 over five years, while the same deposit at 4.50% APY reaches $12,462 — a $441 difference from a gap of less than one percentage point. Over longer horizons the gap widens dramatically, which is why chasing the best APY matters so much for emergency funds, CDs, and any cash you plan to hold for years.
How to use the APY Calculator
- To convert APR to APY: enter the nominal APR and pick a compounding frequency, then press Calculate APY to see the true annual yield plus a comparison table of every frequency.
- To compare two accounts: switch to the Compare Accounts tab and enter your deposit, the number of years, and each account's APY.
- Press Compare to see each account's final balance, total interest earned, and exactly how much more the winner pays you.
- Re-run with your real numbers — small APY differences compound into meaningful dollars over multi-year holds.
Tips for getting the most yield
- Always compare APY, never APR — APY already includes compounding, so it is the honest number.
- Online banks and credit unions typically pay far higher APYs than brick-and-mortar banks; a 0.5-point gap is real money over time.
- Check fees, minimum balances, and early-withdrawal penalties on CDs — a high APY means nothing if fees eat it.
- APYs on savings accounts are variable and can change at any time, while CDs lock your APY for the term.
Why APR alone misleads savers
APR ignores compounding entirely — it is simply the interest rate divided by the number of periods, with no credit for interest-on-interest. Two CDs can advertise identical APRs yet pay different amounts if one compounds monthly and the other daily. Regulations in the US require banks to disclose APY precisely because it prevents this confusion. The catch: APY tells you nothing about fees, tiered rates (where the advertised APY applies only above a high balance), or introductory "teaser" rates that drop after a few months. Read the terms, then let the APY decide between otherwise-equal accounts.
Frequently asked questions
What is the difference between APR and APY?
APR (Annual Percentage Rate) is the nominal yearly interest rate before compounding; APY (Annual Percentage Yield) reflects the real rate you earn after compounding is applied. For the same nominal rate, APY is always equal to or higher than APR, and the gap grows as compounding gets more frequent.
How do you calculate APY from APR?
Use the formula APY = (1 + r/n)^n - 1, where r is the nominal APR as a decimal and n is the number of compounding periods per year (for example, 12 for monthly). A 5% APR compounded monthly becomes about 5.116% APY.
Why does compounding frequency change the APY?
Interest is calculated on a growing balance, so compounding more often means each new interest payment itself starts earning sooner. Daily compounding therefore produces a slightly higher APY than monthly compounding on the same nominal APR.
Is a higher APY always better for a savings account?
For earning money, yes — APY is the true apples-to-apples comparison, so a higher APY on the same deposit earns more over the same period. Still check fees, minimum balances, and withdrawal limits, which can quietly eat into the yield.
All calculations are estimates for personal use. This tool is not financial advice; rates shown are illustrative, not actual bank offers.