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Calculate Retirement: Bengen 4% Rule & FIRE

Calculate how much money you need to retire, whether you are on track, and your safe monthly retirement withdrawal income.

• Verified Financial Math • Zero Telemetry / 100% Private • Instant Client-Side Computation

Interactive Retirement Calculator

How much do I need to retire?

Ready to Compute

Enter your financial parameters below to generate an instant, 100% deterministic breakdown with sensitivity analysis and scenario comparison.

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Mathematical Formulation & Methodology

Decidely executes pure deterministic client-side mathematics. Unlike probabilistic AI models that guess numerical results, every calculation is calculated using standard financial accounting equations:

Nest Egg Required = (Annual Retirement Spending × (1 + Inflation)^YearsToRetire) × 25 (based on the Trinity Study 4% Rule).

Baseline Assumptions & Standards

  • Utilizes the 4% Safe Withdrawal Rule (25x annual spending)
  • Spending adjusted annually for inflation to preserve purchasing power
  • Portfolio invested in diversified equities and fixed income

Worked Example: 32-year-old planning to retire at 65 with $65,000/yr spending

Checking retirement readiness and required nest egg.

Example Inputs

Current Age 32
Retirement Age 65
Current Savings $50,000
Monthly Contribution $750

Calculated Output

Target Nest Egg $1,625,000 (today value)
Projected Portfolio $1,840,000
Status On Track (+$215,000)
Key Financial Takeaway:

Saving $750/month with an existing $50,000 nest egg comfortably funds a $65,000/year lifestyle by age 65.

Empirical Benchmarks Trinity Study & Bengen Rule

Safe Withdrawal Rate (SWR) Longevity Matrix

Historical success rates across variable withdrawal percentages over a 30-year retirement horizon (75% stocks / 25% bonds portfolio adjusted annually for inflation):

Withdrawal Rate Nest Egg Multiplier 30-Yr Portfolio Survival Annual Income per $1M Strategic Profile
3.0% 33.3× Spending 100% Success $30,000 / yr Perpetual / Generational Wealth
3.5% 28.6× Spending 99% Success $35,000 / yr Early Retirement (FIRE 40+ Yrs)
4.0% 25.0× Spending 96% Success $40,000 / yr Standard Bengen Rule Baseline
4.5% 22.2× Spending 86% Success $45,000 / yr Requires Flexible Spending Adjustments
5.0% 20.0× Spending 72% Success $50,000 / yr High Capital Depletion Risk in Bear Markets

Frequently Asked Questions

What is the 4% rule in retirement?

The 4% rule, established by the Trinity Study, indicates you can safely withdraw 4% of your initial retirement portfolio (adjusted for inflation each year) for 30 years with minimal risk of running out of money.

What is FIRE (Financial Independence, Retire Early)?

FIRE is a movement focused on aggressive savings (often 40-60% of income) and low-cost investing to accumulate 25 times annual expenses, achieving financial independence decades ahead of traditional retirement age.

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