FIRE Calculator: When Can You Actually Retire Early?
The FIRE movement promises early retirement. We ran the numbers across 5 countries and 300 simulations each.
What Is FIRE?
FIRE — Financial Independence, Retire Early — is a movement built around aggressive saving (typically 50–70% of income) and investing with the goal of accumulating enough wealth to live off investment returns indefinitely. The standard benchmark is the 4% rule: once your portfolio reaches 25× your annual expenses, you can safely withdraw 4% per year without running out of money.
The 4% rule originates from the Trinity Study (1998), which analyzed 30-year periods of US stock/bond returns. But it has significant limitations that Monte Carlo simulation exposes.
The Problem With the 4% Rule
The 4% rule assumes:
- A 30-year retirement horizon — but if you retire at 35, you need 50+ years of runway
- US market returns — which may not apply to UK, Australian, or emerging market investors
- A fixed withdrawal rate — ignoring that real spending fluctuates with life events
- No major economic regime changes — like the transition from secular bull markets to higher-inflation environments
For early retirees, the 4% rule is optimistic. Monte Carlo simulation paints a more realistic picture.
Our Simulation Setup
We modeled a 30-year-old saving aggressively in 5 different markets:
Results: When Do You Actually Hit FIRE?
🇺🇸 United States
P50 (median): 12.5 years (age 42.5). But the P10 scenario (poor market returns early) pushes this to 18 years (age 48). The P90 case gets there in 9 years. If you're planning to hand in your resignation at 42, understand there's a meaningful probability you won't be ready until 48.
🇬🇧 United Kingdom
P50: 14 years (age 44). ISA allowances (£20K/year tax-free) accelerate accumulation vs taxable accounts, but FTSE returns have historically lagged the S&P, widening the P10–P90 gap.
🇮🇳 India
P50: 11 years (age 41) — the fastest in our dataset, driven by high savings rates and strong equity returns in Indian markets. However, currency devaluation risk and 6–8% inflation make the P10 case much more fragile.
The Real Risk: Sequence of Returns
The biggest risk for early retirees isn't average market performance — it's sequence of returns risk. If you hit a major market downturn in your first 3–5 years of retirement, your portfolio may never recover even if markets average 7% over the full period.
This is exactly what Monte Carlo simulations capture. In our US model, 14% of simulations showed portfolio depletion before age 80 — despite using a “safe” 4% withdrawal rate. For a 50+ year retirement, a 3.25–3.5% withdrawal rate is more appropriate.
Build Your FIRE Plan
Finasim's FIRE Calculator template lets you input your income, savings rate, expected expenses, and country. It runs 300 Monte Carlo simulations and shows you your P10/P50/P90 FIRE date, safe withdrawal rate, and probability of portfolio survival through age 90.