Want the full engine rather than a single identity? The live Monte Carlo demo runs 1,000 seeded paths on a fictional household with no signup. The withdrawal-strategy hub compares all nine rules in one table.
FIRE numbers
Coast FIRE calculator
How much you need invested today for compounding alone to reach your number by your retirement age.
Barista FIRE calculator
The portfolio that covers the gap between your spending and a part-time income, so full-time work can stop.
Lean FIRE calculator
Years of saving to fund a modest retirement number — typically around $40,000 a year.
Fat FIRE calculator
Years of saving to fund a comfortable retirement number — typically $100,000 a year and up.
Retirement math
Safe withdrawal rate
Turn a portfolio into a first-year retirement income, or an income target into the portfolio it needs.
Retirement number calculator
The portfolio that funds a chosen annual spend, and how many years of saving get you there.
Rule of 25 calculator
The 25× (or any multiple) nest egg for a spending target, and the implied withdrawal rate.
How long will my money last calculator
Years a portfolio lasts at a chosen withdrawal, plus a 1,000-path band around that single line.
Flexible spending
Guyton-Klinger calculator
See when guardrails cut or raise spending, and what that does to the portfolio over a chosen horizon.
Vanguard dynamic spending
A target percentage of the current balance, with year-to-year spending changes clamped to a ceiling and a floor.
Endowment spending calculator
Yale’s published rule: 80% of last year’s spending plus 20% of a 5.25% target rate, held inside a 4.0% to 6.5% collar.
Risk-based guardrails calculator
Cut or raise spending when the remaining probability of success leaves a chosen band — not when the withdrawal rate does.
Spending formulas
VPW calculator
Variable percentage withdrawal: spend a rising share of the remaining balance as the horizon shortens.
CAPE withdrawal calculator
Set a first-year withdrawal rate from the current CAPE earnings yield, then inflate that dollar amount.
Merton withdrawal calculator
Merton’s risky share from risk aversion and volatility, then a remaining-horizon annuity at that implied return.
Risk and fees
By the query people type
4% rule calculator
Bengen’s 4% of the starting portfolio as a first-year income, with fees taken off.
Trinity study calculator
The Trinity question: a 4% initial withdrawal for 30 years, reported as a 1,000-path success rate.
FIRE calculator
Spending divided by a withdrawal rate, and years of saving to reach that number.
Monte Carlo retirement calculator
1,000 seeded paths, a success rate, and a band of ending balances. No signup.
Retirement paycheck calculator
Turn a portfolio and a withdrawal rate into a monthly paycheck.
Which retirement guardrails?
Choose Guyton-Klinger rails or risk-based rails, then open the tool that runs them.
Lump sum vs dollar-cost averaging
The same dollars invested today versus spread over years, on one return path.
Real return calculator
Nominal return after inflation, using the Fisher identity, not a subtraction.
Withdrawal order calculator
Taxable, tax-deferred and Roth as three buckets. Which you empty first changes what is left — not a tax engine.
Can I retire calculator
A portfolio, a spend, a horizon, and a 1,000-path success rate.
Savings rate calculator
What fraction of income you save, and how many years that takes to the number.