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S&P 500 Reality Check

What this spend would be worth in 10, 20, 30 years at market returns.

Future value = principal × (1 + return)^years. The default 7% reflects long-run S&P 500 real returns. Raise to 15–20% to model a venture or leveraged business alternative. If the future value exceeds 5× the spend, the opportunity cost is high — the purchase must justify a big gap.

Part of: Saving & Spending Calculators

Start below
Fields marked optional can be skipped; results update as you type
SP500_REALITY_CHECK
Opportunity cost — what this purchase would be if left in the market
$
FUTURE VALUE — 20 YEARS @ 7%
$38,6973.9× the original
COMPOUND GROWTH
— Investment● Current Spend
NOW · $10,000Y20 · $38,697
+10 yrs
$19,672
+20 yrs
$38,697
+30 yrs
$76,123
Opportunity Cost
$28,697
▸ METHODOLOGY
Future value = principal × (1 + return)^years. Default 7% reflects long-run S&P 500 real returns; raise to 15–20% for venture or leveraged business investments. If your proposed spend cannot beat the future-value multiple over the same horizon, it is underperforming the market-neutral alternative.

Before you trust the result

Check the inputs that matter most: dates, rates, units, costs, and any optional fields you skipped. A calculator can only work with the numbers entered here, so use the result as a decision check rather than a final answer when money, health, tax, legal, or safety consequences are involved.

If the result feels surprising, change one input at a time and watch which number moves. That usually shows the real lever behind the decision.

More about this tool

How to use this tool
  1. Enter the proposed Purchase/Investment amount.
  2. Set Time Horizon in years.
  3. Set Expected Return % (default 7, cap commonly 20 for venture).
  4. Read the 10-, 20-, and 30-year future values plus the opportunity-cost delta.

Examples

$10k at 7% for 20 years
Future value ≈ $38.7k — the "$10k purchase" has a ~$28.7k opportunity cost at that horizon.

Next up

Business losing to index? Set the rate that beats it.Minimum Viable Rate → Index winning? Maybe skills pay better than the business.Upskill ROI · Investment Recovery →

Frequently asked questions

› Why 7% as default? Troubleshooting

Roughly the long-run real (inflation-adjusted) return of the S&P 500. Nominal returns are higher; use real for honest comparisons.

› Does this account for taxes?

No — pre-tax figures. In tax-advantaged accounts the numbers hold; in taxable accounts knock 15–25% off the future value.

Tips & related reading

See the Saving & Spending Calculators hub →

Tips & how-tos

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