Investment Calculator

How Investment Returns Work

Investment returns compound over time, meaning you earn returns on your returns. This exponential growth — often called the eighth wonder of the world — is why starting early matters so much. Even small monthly contributions can grow substantially over decades thanks to the compounding effect.

The Compound Growth Formula

FV = PV x (1+r)^n + PMT x ((1+r)^n - 1) / r, where FV = future value, PV = initial investment (present value), PMT = periodic contribution, r = periodic return rate (annual rate / 12 for monthly), and n = total number of periods. For example, $10,000 initial investment with $500/month at 8% annual return over 30 years grows to approximately $780,000.

Historical Average Returns by Asset Class

• US Large-Cap Stocks (S&P 500): ~10% per year (1926-2024)
• US Small-Cap Stocks: ~12% per year, with higher volatility
• International Developed Stocks: ~8% per year
• US Bonds (Aggregate): ~5% per year
• US Treasury Bills (Cash): ~3% per year
• Real Estate (REITs): ~9% per year

Risk vs. Return

Higher expected returns come with higher risk (volatility). Stocks historically outperform bonds over long periods but can lose 30-50% in a single year during bear markets. Diversification across asset classes helps manage risk while pursuing growth. A common guideline is to hold your age in bonds (e.g., 30% bonds at age 30) for appropriate risk management.

The Impact of Starting Early

• Investing $300/month from age 25 to 65 at 8% return: ~$1,050,000
• Investing $300/month from age 35 to 65 at 8% return: ~$440,000
• Investing $600/month from age 35 to 65 at 8% return: ~$880,000 — still less than starting 10 years earlier at half the amount

Tax-Advantaged Investment Accounts (2024)

• 401(k): $23,000 contribution limit ($30,500 if 50+), often with employer match
• Traditional IRA: $7,000 limit ($8,000 if 50+), tax-deductible contributions
• Roth IRA: $7,000 limit ($8,000 if 50+), tax-free withdrawals in retirement
• HSA: $4,150 individual / $8,300 family, triple tax advantage for medical expenses

Important Notes

This calculator shows projected gross returns and does not account for investment fees, taxes, or inflation. Actual net returns will be lower. Keep investment costs low by choosing index funds with expense ratios under 0.20%. Historically, 80-90% of actively managed funds underperform their benchmark index over 15+ year periods. Past performance does not guarantee future results — always invest according to your risk tolerance and time horizon.