FIRE Simulator: Historical Backtest Retirement Calculator
Stress-test your retirement plan against every year of real market history, not a single guessed average return.
- Historical backtest: replays your plan across every rolling window of market history since 1871 to expose sequence-of-returns risk.
- Real terms: every portfolio value and withdrawal is inflation-adjusted to today’s purchasing power.
- 12 withdrawal strategies: the 4% rule, VPW, Guyton-Klinger, CAPE-based and more, each explained below.
- Four asset classes: allocate across stocks, bonds, cash and gold, rebalanced annually.
- Save, share & export: keep a plan in your browser, copy a shareable link, or download the runs as CSV.
With the default plan ($1,000,000 invested, $40,000 a year of spending held constant after inflation, in a portfolio of 80% stocks, 15% bonds and 5% cash), the money lasted all 30 years in 122 of the 125 rolling 30-year windows in US market history between 1871 and 2024. Run the simulator below to test any portfolio, horizon or withdrawal rule against the same record.
How the simulation works & data caveats
This simulator assumes you already have a target portfolio and spending figure to test. If you haven’t worked those out yet, the FIRE plan calculator works out the age you could retire and the pot behind it, with your housing in the picture. Come back here afterwards to stress-test what it gives you. For a shorter exit rather than a full retirement target, the quit-my-job calculator counts the months your current savings buy instead.
The simulator runs a historical rolling-window backtest: it replays your plan as if you had retired at the start of every year in the dataset (1871, 1872, 1873, and so on) and reports how many of those historical retirements survived. That is how it captures sequence-of-returns risk, the danger that a crash early in retirement does far more damage than the same crash later. The sequence of returns risk calculator isolates that effect, replaying one real window forwards and backwards with nothing changed but the order. The same scenario can also be run through the retirement probability calculator, which computes the exact odds of success directly from the return distribution instead of counting historical outcomes.
The engine simulates in nominal terms and then deflates every figure by historical inflation, so all results are shown in real, inflation-adjusted terms: today’s purchasing power. That makes a retirement that started in 1966 directly comparable to one that started in 1982.
Returns come from Robert Shiller’s long-run US dataset for stocks, bond yields and the Consumer Price Index, converted from monthly to annual resolution. Two caveats worth knowing: gold only becomes a meaningful asset from 1971 onward (after the US dollar left the gold standard), so gold-heavy plans are backtested over the shorter 1971+ window; and cash is modelled as a short-term proxy rather than a specific savings product. A high historical success rate is a robustness signal rather than a guarantee: the future can still differ from every past sequence.
Every data source, formula and default across this site is documented on the methodology page.
Choosing your withdrawal strategy
Which withdrawal strategy fits you depends on what you care about most: predictable spending, never running out, maximising lifetime income, or a balance of the three. Find the goal that sounds like you, then expand a strategy to see how it decides each year’s withdrawal, what it trades off, and its pros and cons. For a simpler runway question (how many months or years your current savings last at a fixed spend, without simulating markets), the bag-o-money calculator answers that directly.
I want the most predictable, stable spending
A constant-amount (4% rule) plan pays the same inflation-adjusted amount every year, so the budget never moves with the market.
Constant Amount
The same inflation-adjusted amount every year, regardless of how the market performs.
The rule fixes a first-year withdrawal amount, for example 4% of the starting portfolio, then repeats that exact amount every subsequent year, grown only by realised inflation. This is the classic Bengen "4% rule" and the default most retirement studies benchmark against. The portfolio value never enters the calculation.
What it trades off: Constant-amount withdrawals are the most predictable real income any of these rules produce, and the easiest to budget around. Nothing in the rule reacts to the market, so the portfolio absorbs a bad early sequence on its own, and a good one leaves money unspent.
Pros
- Perfectly stable, predictable real spending
- Simple to understand and follow
- The most widely studied and benchmarked rule
Cons
- Ignores market signals, so it can deplete the portfolio in a bad early sequence
- Leaves large unspent balances in good sequences
- No mechanism to spend more when the portfolio grows
Parameters
This strategy has no adjustable parameters. It runs from your portfolio, allocation, and starting withdrawal alone.
I never want to run out of money
Percent-of-portfolio rules always take a share of what remains, so they cannot fully deplete; the Endowment variant smooths the resulting income.
Percent of Portfolio
A fixed percentage of the current portfolio value, taken again each year as the balance rises and falls.
Each year the rule takes the same percentage, for example 4%, of whatever the portfolio is worth at that moment, so spending moves one-for-one with the balance. Because the withdrawal is always a fraction of what is left, the portfolio can never be fully depleted. Optional floors and ceilings, set in first-year money and grown with inflation, bound how far spending can swing.
What it trades off: Every withdrawal is a share of what remains, so the portfolio cannot be fully depleted and spending self-corrects after a crash. The correction cuts income furthest in the years it is hardest to cut.
Pros
- Mathematically impossible to fully deplete the portfolio
- Spending self-adjusts to market conditions
- Optional floor/ceiling bands tame the volatility
Cons
- Highly variable year-to-year income
- A prolonged downturn forces painful spending cuts
- Hard to budget a household around
Parameters
- Withdrawal percent: The share of the current portfolio withdrawn each year. Higher spends more now but draws the balance down faster after bad years.
- Spending floor (year-1 money, 0 = none): A minimum yearly withdrawal, set in first-year money and grown with inflation, so spending never drops below it. Set 0 to disable the floor.
- Spending ceiling (year-1 money, 0 = none): A maximum yearly withdrawal, set in first-year money and grown with inflation, so spending never rises above it. Set 0 to disable the ceiling.
Endowment Strategy
A weighted blend of last year’s spending and a fresh percent-of-portfolio target, which smooths out the year-to-year swings in spending.
Modelled on how university endowments (the Yale/Tobin rule) spend, this takes a weighted average of last year’s withdrawal and a fresh percent-of-portfolio target. The smoothing weight dampens the year-to-year swings of a pure percentage rule, so a market crash trims spending only gradually instead of all at once.
What it trades off: Blending last year's withdrawal with a fresh percent-of-portfolio target keeps a percentage rule's sustainability while moving income gradually instead of all at once. The same lag means spending trails a recovery as slowly as it trails a crash.
Pros
- Much smoother income than a raw percentage rule
- Never fully depletes the portfolio
- Cushions the impact of any single bad year
Cons
- Adjusts slowly, so it lags big market moves
- Still trends down through a long bear market
- Two inputs (weight and rate) to tune
Parameters
- Smoothing weight (share of last year): How much of each year’s withdrawal is carried over from last year versus a fresh percent-of-portfolio target. Closer to 1 makes income smoother and slower to react.
- Target portfolio percent: The percent-of-portfolio target the smoothing pulls toward each year. Higher raises long-run spending (and how far it can eventually swing).
I want to spend as much as possible over my lifetime
Amortisation rules like VPW, Dynamic SWR, 1/N and Hebeler Autopilot spread the balance across the remaining years, front-loading more spending while still adapting to the market.
Variable Percentage Withdrawal (VPW)
VPW spreads the current portfolio across the remaining years at an assumed return, so the withdrawal rate climbs as the horizon shortens.
VPW (the Bogleheads Variable Percentage Withdrawal method) treats each year like an annuity payment: it spreads the current balance across the years left at an assumed annual return, so the percentage withdrawn climbs as the horizon shortens. Because it recomputes off the live balance every year, it reacts to the market while still front-loading more spending than a flat percentage.
What it trades off: VPW pulls more lifetime spending out of the same portfolio than a flat rule, by lifting the withdrawal percentage as the horizon shortens and recomputing off the live balance each year. Income moves with the portfolio in both directions, and the path hinges on the assumed return.
Pros
- Maximises spending over the full horizon
- Adapts to both market returns and remaining lifespan
- Backed by the well-documented Bogleheads methodology
Cons
- Income is variable and can drop after bad years
- Sensitive to the assumed-return input
- Late-life withdrawal rates get aggressive
Parameters
- Assumed annual return: The yearly return the amortization assumes when spreading the balance over the remaining years. A higher assumption front-loads more spending early (and less later).
Full guide to the Variable Percentage Withdrawal (VPW) strategy
Dynamic SWR
A dynamic safe withdrawal rate: the current balance amortised over the remaining years at a conservative assumed return.
Dynamic SWR uses the same amortisation mechanic as VPW, spreading the live balance across the remaining years, but at a more conservative assumed return, which front-loads less spending and holds more back for later years. Spending still tracks the portfolio, just more cautiously than VPW.
What it trades off: Dynamic SWR runs VPW's amortisation at a more conservative assumed return, holding back more for later years and limiting the damage an over-optimistic return input can do. In strong markets it leaves spending unclaimed.
Pros
- Adaptive like VPW but more conservative
- Lower risk of over-spending early
- Smooths income relative to aggressive rules
Cons
- Leaves more on the table in strong markets
- Still varies with portfolio value
- Depends on the chosen return assumption
Parameters
- Assumed annual return: The yearly return the annuity math assumes when spreading the balance over the remaining years. Lower than VPW by default, so it holds more back for later years.
1/N
The current portfolio divided evenly across the years left in the plan, which runs the balance down to roughly zero at the end.
Each year the withdrawal is the portfolio balance divided by the number of years remaining, so the share taken starts small and grows as the horizon shortens: 1/30 of the balance with 30 years left, 1/2 with two years left. It is a self-liquidating annuity with no insurer and no assumed return behind it. The final year’s withdrawal takes whatever is left.
What it trades off: 1/N spends a balance down to roughly zero by a fixed end date, which is what bridging to a pension or a Social Security start needs and why it leaves nothing for a bequest. Withdrawals grow sharply as the horizon closes, and the final years are the most volatile.
Pros
- Naturally spends the portfolio down over a fixed horizon
- Requires no return assumptions
- Front-loads less than a fixed percentage early on
Cons
- Spending grows sharply and becomes volatile near the end
- Not designed to preserve capital or leave a legacy
- Assumes a hard end date
Parameters
This strategy has no adjustable parameters. It runs from your portfolio, allocation, and starting withdrawal alone.
Hebeler Autopilot II
Three-quarters of last year’s spending blended with a fresh amortised withdrawal off the current balance.
The Autopilot II variant of Henry Hebeler’s method takes a weighted blend: by default 75% of last year’s spending and 25% of a fresh amortised (annuity-style) withdrawal off the current balance. Anchoring most of each year’s withdrawal on last year’s keeps income smooth while still letting the portfolio nudge spending up or down over time.
What it trades off: Anchoring three-quarters of each year's withdrawal on last year's spending produces smooth income that still drifts, slowly and automatically, toward what the portfolio can support. That anchor delays every adjustment, after a crash and after a recovery alike.
Pros
- Smooth, stable year-to-year income
- Still tracks the portfolio over the long run
- Automatic, rules-based adjustment
Cons
- Adapts slowly to sudden market moves
- Can lag a sharp portfolio recovery
- Blend weight and return assumption both matter
Parameters
- Prior-spend weight (share of last year): How much of each year’s withdrawal is anchored to last year’s spending versus a fresh amortized amount. Higher (closer to 1) makes income smoother.
- Assumed annual return: The yearly return the amortized (annuity-style) part of the blend assumes when spreading the balance over the remaining years.
I want steady spending but a higher starting withdrawal
Guardrail rules hold spending steady in normal years and only adjust at set thresholds, supporting a higher initial rate than a rigid plan.
Guyton-Klinger
An inflation-adjusted base plus guardrails that cut or raise spending when the withdrawal rate drifts too far from where it started.
Guyton-Klinger starts from an inflation-adjusted base and then applies guardrails to the withdrawal rate: if a market drop pushes that rate more than a set band above where it started, the Capital Preservation rule cuts spending; if a rising portfolio pulls it the same distance below, the Prosperity rule raises spending. A plan already withdrawing above its starting rate skips its inflation raise. Spending holds steady most years, with occasional corrections.
What it trades off: The guardrails support a higher starting withdrawal than a rigid inflation-adjusted plan, and spending holds steady in the years the rate stays inside its band. Corrections trigger only once the rate has already drifted, so a cut can land in the middle of a bad market.
Pros
- Supports a higher initial withdrawal than the 4% rule
- Stable in normal years, correcting only at the guardrails
- Well-known, decision-rule-based framework
Cons
- Guardrail cuts can arrive at the worst time
- More rules to track than a simple strategy
- Sensitive to the band and adjustment settings
Parameters
- Guardrail band: How far the withdrawal rate may drift from its starting level before a guardrail fires. A wider band means fewer spending adjustments.
- Spending adjustment: How much spending is cut (or raised) when a guardrail fires. Larger values make the occasional correction bigger.
Vanguard Dynamic Spending
A percent-of-portfolio target with a ceiling and a floor on how far spending can move from one year to the next.
Vanguard’s dynamic spending rule aims for a percent-of-portfolio target and then clamps the change: spending can rise only up to a ceiling and fall only to a floor relative to last year’s amount, by default +5% and -2.5%. The target supplies most of the responsiveness of a percentage rule; the clamp supplies the year-to-year stability of guardrails.
What it trades off: Capping the year-to-year change keeps spending tied to the portfolio without letting it swing: both the rise and the fall are bounded and known in advance. In a deep downturn the floor can outpace the portfolio, and in a strong market the ceiling trims the upside.
Pros
- Balances responsiveness with income stability
- Bounded, predictable year-to-year changes
- Backed by Vanguard research
Cons
- The floor can outpace the portfolio in deep downturns
- Caps trim upside in strong markets
- Three inputs to tune (target, ceiling, floor)
Parameters
- Target portfolio percent: The percent-of-portfolio spending target before the ceiling and floor below limit how much it can change year to year.
- Ceiling (max yearly increase): The most spending can rise from one year to the next, as a percent of last year. Caps upside jumps in strong markets.
- Floor (max yearly decrease): The most spending can fall from one year to the next, as a percent of last year. Limits painful cuts after a bad year.
I want a secure baseline plus upside when markets do well
These pair a protected floor with participation in gains: the floor protects the base spending while the gains share adds income in strong years.
Sensible Withdrawals
A low base percentage every year, plus a slice of any real gains the portfolio has made above its starting value.
Sensible Withdrawals pairs a conservative base withdrawal (a small percentage of the current portfolio) with an "extras" cut of the real gains the portfolio has made above its inflation-adjusted starting value. In flat and down years the base is the whole income; in good years the extras cut adds a share of those gains on top.
What it trades off: A low base withdrawal protects the inflation-adjusted principal, and a slice of the real gains above it pays out when markets do well. The base alone is lean in flat years, and the bonus half of the income cannot be budgeted a year ahead.
Pros
- Protects the inflation-adjusted principal
- Shares in market gains without over-committing
- Conservative base keeps the plan resilient
Cons
- The base alone may feel lean in flat markets
- Bonus income is unpredictable
- Two rates to configure
Parameters
- Base withdrawal rate: The share of the portfolio always withdrawn, even in flat or down years.
- Bonus rate on real gains: The share of real gains above the inflation-adjusted starting amount, taken as extra spending in good years.
95% Rule
A percentage of the portfolio, floored at 95% of last year’s nominal spending, so no single year cuts income by more than 5% in nominal terms.
From Bob Clyatt’s "Work Less, Live More", this withdraws a percentage of the current portfolio but floors the result at 95% of the previous year’s nominal withdrawal, so a single down year cuts nominal spending by at most 5%. It pairs the sustainability of a percentage rule with a floor that no single year can breach in nominal terms.
What it trades off: The 95% floor keeps the upside of a percentage rule and puts a hard limit on how fast nominal spending contracts: no year cuts it by more than 5% in nominal terms, however far the portfolio falls. In real (inflation-adjusted) terms the cut can be slightly larger. The floor also draws on a shrinking balance through a long bear market, and spending lags the rebound on the way back up.
Pros
- Caps annual spending cuts at 5%
- Keeps the upside of a percentage rule
- Easy to explain and budget around
Cons
- The floor can slowly erode the portfolio in long bear markets
- Still allows meaningful income variation
- Recovery spending lags the market rebound
Parameters
- Withdrawal percent: The share of the current portfolio targeted each year, before the floor below keeps spending from dropping too far.
- Spending floor (fraction of last year): The lowest nominal spending can fall relative to last year. 0.95 means a bad year can cut nominal spending by at most 5%; the real cut can be slightly larger after inflation.
I want spending that reacts to how expensive the market is
The CAPE-based rule sets the withdrawal rate from stock valuations, spending less when the market is expensive and more when it is cheap.
CAPE-based
A withdrawal rate set from the cyclically-adjusted earnings yield, the inverse of Shiller’s CAPE ratio, so the rate falls when stocks are expensive.
This valuation-aware rule sets the withdrawal rate as a base amount plus a multiple of the cyclically-adjusted earnings yield, which is the inverse of Shiller’s CAPE ratio. When stocks are expensive the CAPE is high, the earnings yield is low, and the rate falls; when stocks are cheap the rate rises. It responds to the sequence-of-returns risk that valuations foreshadow.
What it trades off: Setting the rate from the cyclically-adjusted earnings yield ties spending to how expensive stocks are at retirement, the signal that foreshadows a bad sequence. It cuts withdrawals during a boom, when a cut is hardest to accept, and the result depends on CAPE data and the chosen coefficients.
Pros
- Responds to valuation-driven sequence-of-returns risk
- Spends more when markets are cheap
- Grounded in the widely-cited Shiller CAPE research
Cons
- Depends on CAPE data and the chosen coefficients
- Can feel counterintuitive to cut spending in a boom
- Valuation timing is imperfect
Parameters
- Base withdrawal rate (a): The fixed floor of the rate formula (rate = a + b × CAPE earnings yield), in percentage points. It sets the baseline withdrawal rate before valuations adjust it.
- CAPE earnings-yield weight (b): How strongly cheap markets raise the withdrawal rate. The rate is a + b × the CAPE earnings yield (100 ÷ CAPE), so a higher b lets valuations move spending more.
Frequently asked questions
What is a historical FIRE simulation?
A historical FIRE simulation backtests a retirement plan against every rolling window of real market history. Instead of assuming a single average return, it replays what would have happened starting retirement in 1900, 1901, 1902 and so on, then reports how often the money lasted. It captures the sequence-of-returns risk that average-return calculators miss.
What is a safe withdrawal rate?
A safe withdrawal rate is the percentage of a starting portfolio that can be withdrawn each year with a high historical probability of not running out of money. The classic "4% rule" comes from this research, but the right rate depends on time horizon, asset allocation, and which withdrawal strategy is in play.
Why does this calculator show results in real (inflation-adjusted) dollars?
The simulation runs internally in nominal dollars and then deflates every result by historical inflation, so all portfolio values and spending are shown in today’s purchasing power. Real dollars are what actually matter for a retiree’s standard of living, and they make results from different retirement start years directly comparable.
Which withdrawal strategy should I use?
It depends on priorities. Constant-amount strategies give the most predictable spending; percent-of-portfolio and VPW-style rules maximise lifetime spending but vary with the market; guardrail rules like Guyton-Klinger and Vanguard Dynamic Spending sit in between. The "Help Me Choose" guide on this page narrows it down, and the simulator compares them side by side.
What historical data does the simulator use?
It uses Robert Shiller’s long-run US dataset for stock returns, bond yields, and inflation (CPI), converted from monthly to annual resolution. It also models cash and gold; gold is only meaningful from 1971 onward, after the US dollar left the gold standard, so gold-heavy plans are effectively backtested over the shorter 1971+ window.
Does a high historical success rate guarantee my plan will work?
No. A historical backtest shows how a plan would have fared across past market sequences, including the Great Depression and the 1970s stagflation, but the future can differ from the past. A success rate is a robustness stress-test, not a promise, and any plan is worth revisiting periodically.