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How APY Works
APY (annual percentage yield) is the rate you actually earn in a year once compounding is counted. A nominal rate is quoted before compounding; the effective rate converts it with APY = (1 + r / n) n − 1, where r is the nominal rate and n is the number of compounding periods per year.
Frequency matters more than most people expect. At a 5% nominal rate, compounding annually gives 5.000%, monthly gives 5.116% and daily gives 5.127%. The gap looks small, but it is extra yield on the same quoted rate, which is why institutions advertise APY rather than the nominal rate.
The principal field turns the rate into an outcome: because APY is already effective, a balance simply grows as P × (1 + APY)years. Use this page to put a savings account, a CD and a bond fund on the same footing before you commit money.
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Frequently Asked Questions
What is a good annual return on investments?
Historically, the S&P 500 has returned about 10% annually before inflation, or 7% after inflation. A diversified portfolio of stocks and bonds typically returns 6-8% annually. High-yield savings accounts currently offer 4-5% APY. Your ideal return depends on your risk tolerance, time horizon, and financial goals.
Should I invest in stocks or bonds?
Stocks historically offer higher returns (10% annually) but with more volatility. Bonds provide steadier income (4-6% annually) with less risk. A common approach is the age-based rule: subtract your age from 110 to determine your stock allocation. At age 30, hold 80% stocks and 20% bonds. At 60, hold 50% stocks and 50% bonds.
Why investing on a schedule beats trying to time the market.
Index Funds vs Individual Stocks
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Last verified: October 01, 2026 | Sources: IRS, Census Bureau, Federal Reserve, Insurance Information Institute
Historical Investment Returns by Decade
Decade
S&P 500 Return
Bonds (Aggregate)
Savings (Avg APY)
2000s
-0.95%
+5.7%
3.5%
2010s
+13.6%
+3.9%
0.5%
2020s (so far)
+11.2%
-1.5%
3.8%
1928-2026 avg
+10.5%
+5.0%
3.3%
Alex invests only $60,000 more but ends up with $710,614 more — entirely due to 10 extra years of compounding. Time is the most powerful investing advantage.
5 Investing Mistakes That Cost You Money
2. Trying to time the market. Missing the 10 best days in the market over 20 years cuts returns by more than half.
4. Not diversifying. Putting all money in one stock or sector is gambling, not investing.
5. Panic selling during downturns. The S&P 500 has recovered from every single downturn in history. Selling locks in losses.
PC
Patricia Chen CFP
Financial Planning · Last reviewed: September 2026
Disclaimer: Calculators and tools on this site are for informational purposes only and do not constitute financial, tax, legal, medical, or investment advice. Results are estimates and may not reflect actual rates or terms. Consult a qualified professional before making decisions. Privacy Policy
Where: A = future value, P = principal, r = annual rate, n = compounding periods/year, t = years, PMT = monthly contribution.
Assumptions
Interest compounds monthly (n=12)
Contributions made at end of each month
Rate remains constant over entire period
No taxes or fees deducted
This calculator provides estimates only. Actual investment returns vary and may result in loss of principal.
Terminology
Compound Interest: Interest calculated on both the initial principal and all previously accumulated interest. Creates exponential growth.
Principal: The initial amount invested or deposited before any interest is earned.
APY: Annual Percentage Yield - the real rate of return including compounding effects.
Dollar-Cost Averaging: Investing a fixed amount at regular intervals regardless of market conditions, reducing volatility impact.
Rule of 72: Quick doubling time estimate: divide 72 by your interest rate. At 7%, money doubles in ~10.3 years.
High-Yield Savings: Online bank accounts offering 4-5% APY vs traditional banks at 0.5%.
Input Help
Monthly Contribution: How much you add each month. Even $100/month at 7% grows to $121,997 in 30 years.
WHAT THIS RESULT MEANS
Reading the number
Enter values to see a practical interpretation.
MODELTransparent estimate
The tool uses only the inputs you set, with the formula published below.
LIMITATIONSReal-world results vary
Fees, taxes, provider rules and market movement can shift the outcome.
RELATED KNOWLEDGE
Concepts connected to this tool
Important: These are informational estimates, not financial, investment, tax or legal advice. Run your own numbers with a licensed professional before acting.
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