FIRE retirement tools that use forward-looking data
The 4% rule was based on historical US returns during a period of declining rates and expanding valuations. What happens if the next 30 years look different? Portfolio Lab answers that question using forward-looking capital market assumptions averaged from J.P. Morgan, BlackRock, Research Affiliates and AQR, not historical extrapolation.
Tools built for early retirement planning
Monte Carlo Retirement Simulator
1,000 simulations with Cornish-Fisher fat-tail adjustment. Fan charts, success probability, sequence risk.
Safe Withdrawal Rate Calculator
Withdrawal simulations using 2026 forward-looking assumptions, with explicit survival targets.
Portfolio Optimizer
Find your optimal asset mix across 57 asset classes including Bitcoin.
Bitcoin Retirement Calculator
Model retirement outcomes with different Bitcoin allocations.
Portfolio Backtester
Test how different allocations would have performed historically.
Drawdown Analyzer
Every Bitcoin crash since 2010. How long until recovery?
Why FIRE planners need forward-looking assumptions
FIRE planning has a uniquely long time horizon. If you retire at 35, your portfolio needs to last 50-60 years. Over that timescale, the difference between using historical returns (which bake in a 40-year bond bull market) and forward-looking estimates (which account for current yields and valuations) is enormous.
J.P. Morgan's 2026 Long-Term Capital Market Assumptions project lower returns for US equities and bonds than the historical average. Planning on the historical 8-10% equity return when the forward estimate is lower means your Monte Carlo success probability is overstated. You could be making FIRE decisions based on return expectations that are unlikely to materialize.
Sequence risk and fat tails
The biggest risk in early retirement is not average returns. It is the order of returns. A market crash in your first few years of withdrawal can permanently impair your portfolio, even if average returns recover later.
Portfolio Lab's Monte Carlo simulator uses Cornish-Fisher adjustment, which models the actual shape of return distributions including fat tails and negative skew. Standard simulators assume returns are normally distributed, which understates the probability of exactly the scenarios that destroy FIRE plans.
The Bitcoin question
Should a FIRE portfolio include Bitcoin? The quantitative answer depends on your assumptions. On our own Bitcoin assumption of 15% geometric return with 42.5% volatility (no house publishes one), mean-variance optimization on J.P. Morgan's 2026 dollar table puts the Sharpe-maximising Bitcoin weight at 15% for a conservative 30/60/10 mix and 30% for a balanced 60/30/10 mix; an aggressive 80/20 mix is still improving at the 30% ceiling of the sweep. Those are arithmetic peaks, not recommendations.
The key insight: at a 10% allocation, a 50% Bitcoin crash costs you 5% of total portfolio value. At a 5% allocation, it costs 2.5%. These are survivable drawdowns within a diversified portfolio. The Bitcoin Allocation Calculator shows exactly how different sizing affects your overall risk and return.
How much do you actually need?
The shorthand is the 25x rule: save 25 times your annual spending and a 4% withdrawal rate covers it. But on J.P. Morgan's 2026 assumptions a balanced 60/30/10 mix supports about 3.0 percent over 30 years and 2.0 percent over 40 at 95 percent confidence, net of a 0.5 percent fee, so the real target is nearer 33 to 50 times spending, a meaningful difference when you are deciding whether you can retire yet. Run your own number against forward assumptions rather than the historical 4% shortcut.
For a worked starting point, the retiree portfolio shows a conservative drawdown allocation alongside its supportable withdrawal rate, and the best free retirement calculators guide compares the main options.
Related reading
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Run Monte Carlo simulationFrequently asked questions
What is the safe withdrawal rate for FIRE?
The traditional 4% rule comes from the 1998 Trinity Study using US historical data. Portfolio Lab's updated analysis using J.P. Morgan 2026 forward-looking assumptions suggests the safe withdrawal rate depends heavily on your asset allocation, time horizon, and confidence level. For a 40-year retirement at 95% confidence, net of a 0.5% fee, traditional stock/bond mixes support roughly 2 to 2.5%; relaxing to 90% confidence or adding a modest Bitcoin allocation can push the sustainable rate higher. Model your own mix in the SWR calculator.
How does Monte Carlo simulation help FIRE planning?
Monte Carlo simulation runs thousands of possible market scenarios (not just the average case) to estimate the probability that your savings will last through retirement. Portfolio Lab uses Cornish-Fisher adjustment to account for fat-tail events (crashes), which standard normal-distribution simulators miss.
Should FIRE portfolios include Bitcoin?
On our own Bitcoin assumption of 15% geometric return with 42.5% volatility (no house publishes one), mean-variance optimization on J.P. Morgan's 2026 dollar table puts the Sharpe-maximising Bitcoin weight at 15% for a conservative 30/60/10 mix and 30% for a balanced 60/30/10 mix; an aggressive 80/20 mix is still improving at the 30% ceiling of the sweep. Those are arithmetic peaks, not recommendations. The practical constraint is position sizing: a 10% allocation means a 50% Bitcoin crash costs you 5% of total portfolio value, which is manageable within a diversified FIRE portfolio.
What is the best portfolio for early retirement?
There is no single best portfolio. It depends on your withdrawal rate, time horizon, risk tolerance, and tax situation. Portfolio Lab lets you test different allocations using forward-looking assumptions and Monte Carlo simulation so you can find the mix that works for your specific FIRE plan.