Kefiw

Archived noindex page. Kefiw's public focus is Property decision help.

Archived page

This older Kefiw page is kept for reference, marked noindex, and removed from the primary sitemap. The current Kefiw experience is focused on property decisions: cost, quotes, damage, buying, selling, owning, and packets.

Go to Property

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.

How to use

  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.

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.

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

Relevant links

Related tools

The Value Floor

Is your time worth more than the professional quote? Balance-scale verdict with DIY cost vs outsourcing.

The Crossover

The exact month when a monthly subscription overtakes a one-time lifetime purchase. Opportunity-cost toggle included.

Rent vs Buy Calculator

Estimate the year buying a home becomes cheaper than renting after mortgage interest, maintenance, selling costs, and cash opportunity cost.