Investment Growth Calculator -- Compound Growth

Investment Growth Projector

Enter your initial investment, monthly contributions, expected return rate, and time horizon to project how your portfolio will grow with compound interest.

How Investment Growth Works

Investment growth depends on three key factors: your initial capital, regular contributions, and the power of compound interest. When your returns are reinvested, you begin earning returns on your returns -- this is compounding.

The compound interest formula

FV = P(1 + r/n)^(nt) + PMT x [((1 + r/n)^(nt) - 1) / (r/n)]

Where:

• FV = Future Value (final balance)
• P = Initial investment (principal)
• r = Annual interest rate (decimal)
• n = Compounding frequency per year (12 for monthly)
• t = Number of years
• PMT = Regular contribution per period

This calculator compounds monthly to match how most investment accounts work. Each month, your existing balance grows by 1/12th of the annual rate, and your new contribution is added on top.

The time factor

Time is the single most powerful variable in investing. An investor who starts at 25 with $200/month at 7% will accumulate more by age 65 than someone who starts at 35 with $400/month at the same rate. The extra 10 years of compounding more than makes up for the lower contribution amount. This is why starting early -- even with small amounts -- matters so much.

Understanding inflation adjustment

Nominal returns (before inflation) look impressive, but they overstate your real purchasing power. If your portfolio grows at 7% per year but inflation runs at 3%, your real growth rate is approximately 4%. Toggling the inflation adjustment shows what your future balance is worth in today's dollars, giving a more honest picture of your future wealth.

Typical Return Rates by Asset Class

Based on long-term historical averages. Past performance does not guarantee future results. Returns vary significantly year to year.

Frequently Asked Questions

How does compound interest work for investments?

Compound interest means you earn returns not only on your original investment but also on previously earned returns. Over time, this creates exponential growth -- often called the "snowball effect." The more frequently interest compounds and the longer you invest, the greater the effect.

What is a realistic annual return rate?

The S&P 500 has historically returned about 10% per year before inflation, or roughly 7% after inflation. Conservative portfolios (heavy in bonds) might return 4--6%, balanced portfolios 6--8%, and aggressive all-equity portfolios 8--12%. Past performance does not guarantee future results.

How does inflation affect my investment returns?

Inflation reduces the purchasing power of money over time. A 7% nominal return with 3% inflation gives roughly a 4% real (inflation-adjusted) return. This calculator lets you toggle inflation adjustment to see what your future balance would be worth in today's dollars.

Why are regular contributions so important?

Regular contributions dramatically boost long-term growth because each new contribution also begins compounding. This is sometimes called dollar-cost averaging. Even modest monthly additions can result in a significantly larger portfolio over decades compared to a one-time lump sum.

What is the difference between the three scenarios?

The conservative scenario (5%) approximates a portfolio heavy in bonds and stable assets. The moderate scenario (7%) approximates a balanced portfolio of stocks and bonds. The aggressive scenario (10%) approximates a portfolio of primarily equities like index funds. Your actual return will depend on your specific asset allocation and market conditions.

Does this calculator account for taxes?

No. This calculator shows pre-tax growth. In a tax-advantaged account (401k, IRA, Roth IRA), taxes may be deferred or eliminated. In a taxable brokerage account, capital gains and dividends are taxed annually or upon sale. Consult a tax professional for specific guidance.

Does this calculator store my data?

No. All calculations run entirely in your browser. No data is sent to any server, and nothing is stored.

Related Tools

• Compound Interest Calculator -- calculate compound growth with different frequencies
• Retirement Savings Calculator -- project retirement savings with 4% rule analysis
• 401(k) Calculator -- estimate 401(k) growth with employer match
• FIRE Calculator -- calculate your path to financial independence
• Savings Goal Calculator -- estimate time to reach a savings target
• Inflation Calculator -- see how inflation affects purchasing power

Privacy & Limitations

Privacy: This calculator runs entirely in your browser. No financial data -- including amounts, rates, or projections -- is transmitted or stored anywhere.

Limitations: This calculator assumes a constant rate of return and does not account for market volatility, taxes, fees, or varying contribution amounts. Real-world returns fluctuate year to year. Use these projections as a planning guide, not a guarantee. This is not financial advice.

Investment Growth Calculator FAQ