Investment Calculator
Project how a one-time lump-sum investment grows at any annual return rate over any time horizon.
How to use this investment calculator
- 1Enter your investment amount.
- 2Enter the expected annual return. Use 7% for broad stock market index funds (historical real return); 10% for nominal; 4–5% for bonds.
- 3Enter the number of years you will hold the investment.
- 4Try different return rates to see how sensitive your outcome is to return assumptions.
How it's calculated
FV = P × (1 + r)^t with annual compounding.
About the Investment Calculator
Lump-sum investment projections reveal the transformative power of time in the market. A single $10,000 investment at age 25, never added to, grows to approximately $217,000 by age 65 at 8% return. The same $10,000 invested at age 45 grows to only $46,600 — 20 fewer years of compounding reduces the final value by 78%.
This is the mathematical argument for starting early even with small amounts. A 22-year-old with $1,000 to invest who earns 8% annually has a 43-year runway to retirement at 65. That $1,000 becomes $24,650 — a 24.6× multiple. The same 8% return for a 45-year-old with a 20-year horizon turns $1,000 into $4,661 — a 4.7× multiple. The 22-year-old's money works 5× harder simply because of time.
For lump-sum investments, the choice of investment vehicle matters enormously for after-tax returns. Index funds with expense ratios of 0.03–0.10% versus actively managed funds charging 1–1.5% represent a 1–1.5% annual return advantage for index funds. On a $50,000 investment over 30 years at 8% base return: the index fund portfolio grows to approximately $503,000; the 1.5%-fee active fund grows to approximately $362,000 — a $141,000 difference from fees alone. This is why Warren Buffett has repeatedly advised individual investors to use low-cost index funds rather than active management.
Frequently asked questions
What is a realistic expected return for stock market investments?
The S&P 500 has returned approximately 10% per year nominally (before inflation) since 1926, and about 7% per year in real terms (after inflation). Diversified global portfolios have returned slightly less. Bonds have returned 3–5% nominally. A 60/40 stock/bond portfolio has historically returned approximately 7–8% nominally. For projections, use 7% real return for long-term stock-heavy portfolios, 5% for balanced portfolios, and 3–4% for conservative fixed-income portfolios. Always also run projections at lower rates (4–5%) to stress-test your plan.
How does investment return compound over long periods?
Compound growth is nonlinear and accelerates over time. $10,000 at 8% annual return: after 10 years = $21,589, after 20 years = $46,610, after 30 years = $100,627, after 40 years = $217,245. Notice that the money grew by $11,589 in the first 10 years but by $116,618 in the last 10 years — 10 times more growth in the same time period. This acceleration is why investment holding period matters more than almost any other variable. The doubling time at 8% is approximately 9 years (Rule of 72). Each doubling doubles all previous growth.
Should I invest a lump sum all at once or spread it out?
Historical data from Vanguard and other research sources consistently shows that lump-sum investing beats dollar-cost averaging (spreading investments over time) approximately 68% of the time over 10-year periods, because markets rise more than they fall. The intuition: money invested sooner has more time to compound. The exception: if markets are at historically extreme valuations or you have strong reason to believe near-term volatility is high, spreading over 6–12 months reduces regret risk. For most people with a 10+ year horizon, investing the full lump sum immediately is the mathematically expected-value-maximizing choice.