FIRE Calculator
Find your Financial Independence number, exact Freedom Day date, and Monte Carlo survival rate. 4 FIRE types — Lean, Regular, Fat, Coast. Free, no signup.
Last reviewed: March 2026
What Is the FIRE Movement?
FIRE — Financial Independence, Retire Early — is a movement centered on saving aggressively (typically 50–70% of income) to build a portfolio large enough to sustain your lifestyle indefinitely from investment returns alone. The core math is simple: save until your portfolio is 25× your annual expenses (the "4% rule"), then retire.
The movement has grown into a community of millions (r/financialindependence has 2.3M members) with variants including Lean FIRE (minimal spending), Fat FIRE (full lifestyle), Barista FIRE (part-time work covers some expenses), and Coast FI (stop saving and let compounding finish the job).
How to Calculate Your FIRE Number
The FIRE Formula
FI Number = Annual Expenses ÷ Safe Withdrawal Rate
Example: $50,000/yr expenses ÷ 0.04 = $1,250,000 FI Number
The 4% rule — from the 1994 Trinity Study — found that a 60/40 portfolio could support 4% annual withdrawals over 30 years in 95%+ of historical market scenarios. For early retirees planning 40–50 year retirements, a 3.5% SWR is more conservative.
Once you have your FI number, your years-to-FIRE depends on your savings rate. The Shockingly Simple Math of Early Retirement shows that a 50% savings rate means FIRE in ~17 years; 60% means ~12 years; 75% means ~7 years.
The 4 Types of FIRE — Which Path Is Right for You?
Lean FIRE
Retire on 50% of average US expenses (~$25,000/year). Maximum frugality. FI number ≈ 12.5× current expenses. Best for: minimalists, geographic arbitrageurs, those valuing freedom above lifestyle.
Regular FIRE
Retire maintaining your current lifestyle. FI number = 25× current annual expenses (4% rule). The classic FIRE target — retire without changing your spending habits.
Fat FIRE
Retire with 150%+ of current lifestyle expenses — luxury, travel, private schools. FI number ≈ 37.5× current expenses. Best for: high earners who don't want to compromise lifestyle.
Coast FI
You've saved enough that compound growth alone reaches your FI number by age 65 — no more contributions required. You can "coast" with lower-stress work, cover current expenses without saving, and let time do the heavy lifting.
The Savings Rate Is Your Superpower
Your savings rate — the percentage of income you invest — is the single biggest lever in your FIRE timeline. Even small increases have dramatic effects:
Assumes 7% real returns, starting from $0. Source: MMM "Shockingly Simple Math".
What Is Monte Carlo Simulation for Retirement?
Monte Carlo simulation runs thousands of randomized market scenarios to test your plan's robustness. Instead of assuming a steady 7% annual return, it uses historical volatility (S&P 500 std dev ≈ 17%) to simulate good years, bad years, and devastating crashes in sequence.
The most dangerous scenario for FIRE is a major crash in your first 3–5 years of retirement — called sequence-of-returns risk. Monte Carlo reveals this: a plan that "works" on average may only survive 75% of scenarios when you account for bad timing.
Most FIRE planners target 90%+ Monte Carlo survival. The FIRE community generally considers 95%+ "bulletproof." This calculator runs 1,000 simulations instantly in your browser.
Methodology & Assumptions
This calculator uses an iterative year-by-year simulation (not closed-form), which handles growing income, increasing expenses, and Social Security income more accurately than simple formulas. The accumulation phase projects your portfolio with real annual returns applied to the year-end balance plus contributions. The drawdown phase models annual withdrawals reduced by Social Security and part-time income.
Monte Carlo uses Box-Muller transformed Gaussian random variables with mean = your expected return and standard deviation = 17% (S&P 500 historical). All calculations run entirely in your browser. No financial data leaves your device.
Frequently Asked Questions
What is the FIRE number formula?
FIRE number = Annual expenses ÷ Safe withdrawal rate. Using the 4% rule: $50,000/year × 25 = $1,250,000. At this portfolio size, the "4% rule" suggests you can withdraw $50,000/year indefinitely.
What is Coast FI?
Coast FI is when your current investments will grow to your full FIRE number by age 65 without any additional contributions. You can "coast" — reduce savings, work part-time, or change careers — and still retire comfortably.
Should I use the 4% or 3.5% rule?
The 4% rule targets 30-year retirements. For early retirement (40+ year horizon), 3.5% or 3.25% is more conservative. This calculator lets you set any SWR from 2.5% to 6% and see the impact instantly.
What is sequence of returns risk?
If markets crash in your first 1–5 years of retirement, large withdrawals from a declining portfolio can permanently deplete it — even if markets recover fully later. The 1,000-simulation Monte Carlo in this calculator specifically models this risk.
What savings rate do I need to retire in 10 years?
To retire in approximately 10 years from a zero base at 7% real returns, you need roughly a 65% savings rate. Starting with a significant portfolio (e.g., 5 years of expenses already saved) reduces the required savings rate significantly. Use the tool to see your specific numbers.