Investment Calculator Project growth of lump sums, monthly contributions, or goal-based plans — with inflation, taxes, an...
Investment Calculator
Project growth of lump sums, monthly contributions, or goal-based plans — with inflation, taxes, and realistic market assumptions.
Historical U.S. Market Returns (1928–2024, Source: NYU Stern):
- S&P 500 (Stocks): 10.1% nominal, 7.0% real (after 3.1% inflation)
- Long-Term Gov’t Bonds: 5.5% nominal, 2.4% real
- 60/40 Portfolio: 9.1% nominal, 6.1% real
Important Notes:
- These are *long-term averages* — individual decades vary wildly (e.g., 2000s: 1.1% real return; 2010s: 13.6%).
- Future returns may be lower due to high valuations (CAPE ratio ~30 vs. historical 16).
- “Expected return” should reflect *your* asset allocation — not just stocks.
Small costs compound dramatically over time:
- Expense Ratios: A 1% annual fee on a $100K portfolio @ 7% return reduces 30-year value by **28%** ($761K → $549K).
- Taxes: In a taxable account, 15% LTCG tax + 3.8% NIIT = ~19% tax on gains → cuts effective return by ~1.3%.
- Behavioral Losses: Dalbar study shows average investor underperforms S&P 500 by 4–6% annually due to timing errors.
- Inflation: 3% inflation means $1M in 30 years has the purchasing power of **$412,000 today**.
✅ Solutions: Use low-cost index funds (e.g., VTI: 0.03% fee), tax-advantaged accounts, and stay invested.
Case Study: $500/month for 30 years
- Contributions: $180,000
- @ 5% return: $416,000
- @ 7% return: $585,000
- @ 9% return: $827,000
→ A 2% difference = **$242,000 more** — enough to fund 6 years of retirement.
Warren Buffett’s secret: 99% of his $130B net worth was built after age 50 — thanks to 60+ years of ~20% compounding.
📉 Rule of 72: 72 ÷ annual return = years to double. At 7%: **10.3 years** to double → 30 years = ~3 doubles = 8× growth ($10K → $80K).
➡️ Lump Sum
Model inheritance, bonus, or settlement growth.
➡️ Regular Contributions
Project retirement savings (e.g., $500/mo for 30 years).
➡️ Goal-Based
“How much to save monthly to reach $1M in 25 years?”
Pro Tips:
- Use *real* (inflation-adjusted) return for long-term planning (e.g., 7% nominal − 3% inflation = 4% real).
- Select account type to see after-tax impact (Traditional vs. Roth vs. taxable).
- Switch to Semi-Log chart to see exponential growth clearly.
Note: Assumes constant return. Real markets fluctuate — use as a planning tool, not a guarantee.