← Back to tools

FIRE calculator

Run a 1,000-path Monte Carlo simulation on your savings, contributions, and target retirement age. See how lean, base, and fat spending levels change your odds of the money lasting. Households often use this to compare scenarios — it is an educational model, not financial advice.

Monte Carlo simulation (1,000 runs) · lean / base / fat spending scenarios · example values pre-filled

Using medium risk tier
70% / 30%

Growth: 70% stocks / 25% bonds / 5% cash · ~4.5% real return · ~13.0% volatility

FI Number

$1.0M

ScenarioWithdrawalSuccess
Lean (80%)$32k/yr3.2% of FI # what is this?98%
Base (100%)$40k/yr4.0% of FI # what is this?96%
Fat (125%)$50k/yr5.0% of FI # what is this?91%

1,000 Monte Carlo runs · median (p50) values in today's dollars · inflation-adjusted returns · what does this mean?

96% success — solid plan

Across 1,000 simulated market sequences, this portfolio funded the base spending level in 96% of futures through age 95. The FI Number ($1.0M) is the savings target at the base withdrawal rate.

Key numbers

• 25% of the way to your FI number — $750k to go

• At 7% returns, projected to reach FI number at age 40

• Median scenario: $19.1M remaining at age 95

• In nominal terms: $40k/yr today ≈ $62k/yr in 15 years at 3% inflation

• Est. federal bracket on base: ~12% (2025 IRS rates, standard deduction — verify with a tax professional)

Insights

✓Strong simulated success rate

The base scenario shows a success rate of 96%. Research suggests that plans at or above 85% have historically demonstrated robust survivability across a wide range of market conditions.

✓Aggressive savings rate

The implied savings rate is approximately 50%. FIRE-oriented households commonly target 50%+ savings rates to accelerate portfolio growth. This is well above the general 15–20% benchmark.

ℹConservative withdrawal rate

The implied withdrawal rate is 2.4%, which is below the historical 4% safe withdrawal benchmark. This provides an additional margin of safety.

Compare pre-computed scenarios →

This calculator is an educational tool, not personalized financial, tax, or legal advice. Monte Carlo results — and the bracket estimate above — are illustrations based on historical return and current tax assumptions; past performance does not predict future results, and actual outcomes vary. For guidance specific to your situation, households often consult a licensed financial advisor or tax professional.

Want Social Security, pensions, and a healthcare bridge modeled too? Run a full Traditional simulation on the dashboard →

Frequently asked questions

How does the FIRE calculator work?
It runs a 1,000-path Monte Carlo simulation on your current savings, annual contributions, and target retirement age, then reports the probability your portfolio lasts to your planning age under lean, base, and higher spending levels. Returns are sampled from 156 years of historical market data.
What is a FIRE number?
A FIRE (Financial Independence, Retire Early) number is the portfolio size at which investment returns can sustainably cover annual spending. A common rule of thumb is 25 times annual expenses (a 4% withdrawal rate), though the sustainable rate varies with time horizon, allocation, and market conditions — which is what the simulation estimates directly.
How accurate is a FIRE projection?
No projection can predict the future, but sampling across about 1,000 historical market sequences produces a distribution of outcomes rather than a single guess. The success rate reflects how often a plan survived historically-shaped conditions; it is an educational estimate, not a promise of a specific result.