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How Long Will My Money Last? Simulator The Brutal Math of Inflation vs. Withdrawals , The 4% rule, and market returns.

You've built the nest egg. Now the real question: will it survive you? Most calculators ignore the silent killer—inflation-adjusted spending. One shows you running out at 78. The other shows you safe until 95. The difference isn't luck. It's math.

4% Rule Inflation-Adjusted SWP Portfolio Longevity

Simulation Inputs

$
$

~4% annually ($40k/year)

%
%
years

Depletion Risk

Year 28

Fixed 4% strategy

Safe Until

Year 40+

With inflation adj.

Portfolio Longevity Projection

4% Fixed
Inflation Adj.

Depletion Event: Year 28

Fixed withdrawals don't scale

Sustainable: Year 40+

Purchasing power preserved

Year 0 Year 10 Year 20 Year 30 Year 40

What The Numbers Actually Mean

⚠

The 4% Fixed Trap

Year 1 Buying Power $40,000
Year 20 Buying Power $22,103
Portfolio Depletion Year 28

Fixed withdrawals feel safe psychologically but destroy purchasing power. By year 20, your $40k behaves like $22k. The portfolio appears stable—until it collapses rapidly in the final decade.

✓

Inflation-Adjusted SWP

Year 1 Withdrawal $40,000
Year 20 Withdrawal $72,244
Sustainability 40+ Years

Starting at 3.5% with annual inflation adjustments preserves lifestyle. Yes, you withdraw more nominally over time, but your purchasing power remains constant. The portfolio endures because withdrawals scale with reality.

Stress Test: Variable Scenarios

Scenario Return Rate Inflation Fixed 4% Lasts Inflation-Adj Lasts Risk Level
Bull Market 9% 2% 35 years 50+ years Low
Historical Avg 7% 3% 28 years 40+ years Medium
Stagflation 5% 6% 18 years 32 years Critical
Sequence Risk 4% 3% 15 years 24 years High

*Sequence of returns risk assumes poor market performance in first 5 years of retirement. This is the most dangerous period for any withdrawal strategy.

The Fine Print: What This Simulator Assumes

Market Assumptions

  • › Returns are modeled as consistent averages, not volatile sequences
  • › No adjustment for bear markets, recessions, or black swan events
  • › Tax implications not included—withdrawals are pre-tax estimates

Behavioral Realities

  • › Assumes rigid adherence to strategy (humans panic sell)
  • › No additional income (Social Security, part-time work) factored
  • › Healthcare costs and long-term care not modeled

Bottom line: This tool models mathematical probability, not destiny. Use it to identify danger zones (where the red line drops) rather than precise dates. Real retirement requires flexibility, not rigid formulas.

Test Your Specific Numbers

The examples above use $1M portfolios. Your situation is different. Adjust the return rates, experiment with 3.5% vs 4% withdrawals, see exactly where your depletion event occurs.

Pro tip: Toggle between "Fixed 4%" and "Inflation Adjusted" to see the divergence in real-time.

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Critical Questions

The classic 4% rule assumes you increase withdrawals by inflation annually. However, if you fix your withdrawal at 4% of the initial portfolio (without inflation adjustments), your purchasing power erodes. In 6% inflation scenarios, a fixed $40k withdrawal becomes effectively $20k in buying power within 12 years. The portfolio balance looks stable, but you're getting poorer in real terms.
At $1.5M, a 4% withdrawal equals $60k annually ($5k/month). With 7% returns and 3% inflation: Fixed 4% lasts ~32 years before depletion. Inflation-adjusted 4% lasts indefinitely in most scenarios. The key variable is your withdrawal flexibility—can you reduce to 3% during market downturns? That single change extends portfolio life by 15+ years.
The 4% rule is a specific SWP (Systematic Withdrawal Plan) strategy. SWP is the broader category—any method of regularly selling portfolio assets to generate income. The 4% rule specifies: withdraw 4% of initial balance in year 1, then adjust that dollar amount for inflation annually. Other SWP strategies include fixed percentage (withdraw 4% of current balance yearly), guardrails (reduce spending after bad years), or dynamic strategies based on market valuations.
$800k at 3.5% generates $28,000 annually ($2,333/month). Whether this works depends on your burn rate and location. In low cost-of-living areas with paid-off housing, this is viable. In major cities, it's tight. The 3.5% rate provides higher safety margins than 4%, especially for 50+ year retirements. Consider geo-arbitrage or part-time income to bridge gaps during market downturns rather than rigidly following any percentage.
Sequence of returns risk is the biggest threat to early retirees. A 30% drop in year 1, combined with fixed withdrawals, permanently impairs the portfolio. $1M becomes $700k; your $40k withdrawal is now 5.7% of the portfolio. Even if markets recover, you've sold shares at the bottom. The solution: flexible spending rules (guardrails), cash buffers (2-3 years expenses in bonds), or part-time income during downturns. The simulator shows average returns—real life requires contingency plans.