Calculate your investment growth with compound interest. See how your money can grow over time with regular contributions and different compounding frequencies.
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Disclaimer
This calculator provides estimates for informational purposes only. Results may vary based on individual circumstances. Consult a qualified financial professional or tax advisor for personalized advice. Tax rates and brackets are based on 2026 data and are subject to change.
Time in the Market vs Timing the Market — The Numbers
$500/month invested starting at age 25 at 7% average annual return produces approximately $1.2 million by age 65. Starting at age 35 with the same amount produces $567,000 — less than half — despite only a 10-year difference in start date. Those 10 extra years of compounding contribute $633,000 of additional wealth. As calculators.org notes, inflation also matters: a 10% nominal return during 3% inflation is only a 7% real return. This calculator accounts for both nominal growth and optional inflation adjustment so your projections reflect real purchasing power.
How to Use the Investment Calculator
Enter your initial investment (can be zero), monthly contribution, expected annual return, and investment period in years. Optionally add an annual inflation rate to see inflation-adjusted (real) returns. The calculator shows total value at end of period, total amount contributed, total growth from returns, and a year-by-year table. Run multiple scenarios by changing the return rate to see optimistic (10%), moderate (7%), and conservative (5%) outcomes side by side.
Frequently Asked Questions
Historical averages: S&P 500 total return ~10% nominal, ~7% after inflation. Balanced 60/40 portfolio: ~7% nominal, ~4% real. Bonds: ~4–5% nominal. High-yield savings: 4–5% (but not inflation-beating after taxes). For long-term projections, most financial planners use 6–7% as a middle-ground real return for stock-heavy portfolios.
A $60,000 lump sum invested at 7% for 20 years grows to $232,000. Investing $250/month for 20 years ($60,000 total) at 7% grows to $130,000 — less total growth, but the lump sum requires having $60,000 upfront. For most people, regular monthly contributions are more realistic and still build substantial wealth through compounding.
Dollar-cost averaging means investing a fixed dollar amount at regular intervals regardless of market price. When markets are down, you automatically buy more shares; when up, you buy fewer. Over time this smooths out purchase price. Studies show DCA performs similarly to lump sum investing over the long term, but reduces the risk of investing everything right before a market drop.
Inflation erodes purchasing power. A 10% nominal return during 3% inflation is only a 7% real return — meaning your money buys 7% more purchasing power per year, not 10%. Over 30 years at 10% nominal: $100 becomes $1,745. After 3% inflation: equivalent to $720 in today's dollars. Always look at inflation-adjusted returns for long-term planning.
A common rule is to subtract your age from 110 to get the stock percentage (so at 40, hold 70% stocks, 30% bonds). As you approach retirement (10 years out), gradually shift toward more bonds to reduce volatility. The goal is to avoid a large market drop right before you need the money — sequence of returns risk is the biggest threat to late-stage portfolios.
