Project investment growth with compound interest, monthly contributions, and inflation adjustment. Includes year-by-year table showing how your portfolio builds over time.
Growth projection with contributions, inflation & taxes
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This investment calculator helps you project stock market returns and portfolio growth using realistic return assumptions. The S&P 500 has averaged roughly 10% annual return before inflation from 1957 to 2024 — about 7% after adjusting for inflation. Using 7%–8% as a planning rate for a diversified stock portfolio is reasonable for long-term projections. Plug in $10,000 initial investment, $500 monthly contributions, and 8% return over 20 years and you get a projected balance of around $315,000 — with about $110,000 of actual contributions and $205,000 in compound growth.
Dollar-cost averaging — investing a fixed dollar amount on a regular schedule regardless of market conditions — is one of the most powerful tools for US investors. When prices drop, your $500 buys more shares. When prices rise, your existing shares gain value. Over long periods, DCA removes the pressure of timing the market and smooths out volatility. The inflation adjustment in this calculator shows what your future portfolio is worth in today's dollars, which is the number that actually matters for retirement income planning. A $600,000 nominal balance in 20 years at 3% inflation represents about $330,000 of today's purchasing power.
The S&P 500 has returned roughly 10% annually on average since 1957. Over any 20+ year period in US history, the market has never delivered a negative return — though individual years vary wildly from +30% to -40%.
Investing $500/month consistently through a market crash means buying more shares at lower prices. The investor who kept buying through 2008–2009 and 2020 saw dramatically better outcomes than one who paused or sold.
At 3% annual inflation, $1 million in 25 years is worth about $478,000 in today's dollars. Always view projected retirement balances in real (inflation-adjusted) terms to avoid being misled by large nominal numbers.
Investing $300/month from age 25 to 65 at 8% grows to $1.06M. Starting at 35 with the same plan grows to only $440K. The 10-year head start is worth more than $600,000 — time is the investor's greatest advantage.