Guide
How FireClarity works
From choosing a strategy to interpreting your Monte Carlo results — here's how to get the most out of every calculator.
Choose your FIRE strategy
Not all FIRE paths are the same. The right strategy depends on your timeline, lifestyle preferences, and income flexibility.
Save 25× annual expenses. Retire completely. Suitable if you want a clean break from work.
Retire early and bridge the gap until your state pension arrives. Common in Europe where pensions start at 64–67.
Semi-retire with part-time work. Your income covers some expenses, so you need a much smaller portfolio.
Stop adding to savings once your portfolio is big enough to compound to your FIRE number by retirement age.
Retire to a country with a lower cost of living. A smaller FIRE number means years less work.
Enter your numbers
Each calculator has accordion input sections. You don't need to fill every field — defaults are sensible starting points.
Current age, retirement age, and how long to simulate (usually to age 90–95).
How much you have invested today, and how much you save each month before retirement.
Your expected monthly spend in retirement. Use the country presets as a starting point.
Nominal return (7% default) and inflation (2% default). Use inflation-adjusted (real) mode for the clearest results — all values will be in today's purchasing power.
Add state pension, rental income, or part-time work as income streams. Each has a start age and optional end age.
Read the simulation results
The results panel updates instantly as you change any input.
A five-tier rating from Extremely Safe to Fails, based on your end portfolio, minimum portfolio, and number of years near zero.
Visualises the accumulation phase (growing) and the drawdown phase (declining). Vertical lines mark retirement and pension ages.
Every year of the simulation in detail: portfolio start/end, contributions, growth, expenses, pension income, net withdrawal. Exportable to CSV.
Run Monte Carlo simulation
The deterministic simulation uses a fixed annual return. Real markets are volatile — a single bad decade early in retirement can derail even a well-funded plan.
The Monte Carlo simulation runs your plan through 1,000 randomly generated return sequences, each modelled on your assumed average return with ±15% annual volatility (typical for a global equity portfolio). The result is a success probability: the percentage of scenarios where your portfolio survives to your end age.
Rule of thumb: An 85%+ success rate is generally considered solid. Below 70% suggests the plan is fragile and worth stress-testing with the break-point analysis.
Use the break-point analysis
This section answers the most actionable questions in retirement planning:
- 🚀If the plan succeeds: could you retire even earlier?
- 📊If the plan succeeds: how much more could you spend?
- 📉If the plan succeeds: what is the minimum return rate you can survive on?
- 💰If the plan fails: how much more do you need at retirement?
- ✂️If the plan fails: how much do you need to cut spending?
Each insight is calculated with a binary search — the exact threshold where the plan tips from success to failure.
Ready to plan your FIRE?
It takes about 2 minutes to get a full simulation for your situation.
Open the calculator →