Your retirement plan, tested against 5,000 different markets.
Not a fixed 7% return: crashes, inflation, tax brackets and the order you draw from each account. See how often your money lasts.
$120,000 invested. Saves $1,500/month until 55, then spends $2,000/month in today’s money until 95.
- P90 · optimistic
- $7.3M
- P50 · median
- $1.1M
- P10 · pessimistic
- runs out at 80
Real taxes
Progressive capital-gains brackets by country, unrealised gains, FIFO and three account types.
History or chance
Pure Monte Carlo or real 1950–2020 blocks from the US, Europe, Japan and the UK.
Verified maths
39 checks against exact formulas. Methodology →
Try your own numbers
A quick projection that runs in your browser. For taxes, pensions and withdrawal strategies, open the full simulator.
After 20 years
Not inflation-adjusted (nominal)
Purchasing power (real)
3,000 universes in your browser. No taxes or withdrawals. The full simulator adds taxes, couples and withdrawal strategies.
Open full simulator with these inputsHow long until you reach your goal?
Indicative estimate using compound interest (fixed return). For volatility, taxes and P10/P50/P90 scenarios, use the full simulator.
Estimated time (deterministic scenario)
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Excludes volatility and taxes. For guidance only.
Academic rigour, not naive estimates
Traditional calculators assume fixed returns. Reality is volatile. That's why this simulator generates thousands of trajectories with real data.
- Jordà-Schularick-Taylor database (London School of Economics / Berkeley)
- Markowitz's Modern Portfolio Theory for correlations
- Historical Block Sampling 1950-2020 (modern era)
- C++ engine — 5,000 trajectories in seconds
- Real FIFO tax accounting, not simplistic averages
What people usually ask
Is it really free? Is there a paid version?
Yes, completely free with no sign-up. There's no hidden paid tier either. If you want to save simulations in the cloud and use the AI advisor you can sign in with Google, but every calculation feature is available without an account.
What's the difference between pure Monte Carlo and historical mode?
Custom mode generates random returns from a normal (Gaussian) distribution with the mean return and volatility you define. Historical mode extracts real years from 1950-2020 while preserving the correlation between stocks, bonds, inflation and exchange rates. Both are useful, but historical is the institutional standard to validate retirement plans.
Is my data stored or sent to any server?
Not by default. The simulation runs in your browser via WebAssembly compiled from C++. Only if you choose to save a plan or request an AI diagnosis do we send the data encrypted to our servers (Supabase + Gemini).
Which countries does the tax modelling cover?
Built-in templates for Spain, USA, UK, Germany, France, Italy, Portugal, Ireland, Switzerland, Austria and Sweden, all with editable progressive brackets. You can also enter manual rates if your jurisdiction isn't on the list.
What do the P10, P50 and P90 percentiles mean?
P50 is the median scenario: half of the simulations end with more capital and half with less. P90 represents a strongly bullish market (only 10% of scenarios were better). P10 is the pessimistic scenario — a lost decade of crises. If your plan survives P10, it's exceptionally robust.
Your financial independence starts now
Three minutes to find out whether your FIRE plan really works. No commitments, no sign-ups, no credit cards.
Start free simulationRuns 100% in your browser · We don't store your data without your permission