Retirement simulator · Monte Carlo

Will your savings last through your whole retirement?

NestEggSim simulates 1,000 possible futures of your portfolio and shows how resilient your plan really is — before you decide.

Your data never leaves your browser

The simulation runs locally, in WebAssembly. No accounts, nothing sent to a server — it even works offline, on a plane.

Build your own plan →

Sample plan preview

age: 35 savings: 300,000 zł contributions: +3,000 zł/mo retirement: 65 withdrawals: 5,000 zł/mo (real) strategy: stocks → 60/40

1,000 Monte Carlo paths, computed in your browser. No sign-up, done in seconds.

Portfolio value (nominal) · median, P25–P75 and P10–P90 bands

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This is just the start: plug in your own numbers, add accounts, goals and taxes.

Extend this plan

Private by default

No account, nothing uploaded. The whole simulation engine runs in your browser — your wealth stays with you.

Instead of a single “average” forecast — 1,000 Monte Carlo paths and the full distribution: median, percentiles, capital-depletion risk.

Every run has a seed. The same plan with the same seed always gives an identical result — save it, compare it, share it as a link.

One click — no forms, no sign-up. A result in seconds, computed locally.

Open the plan in the app: change your age, savings and accounts — the result recomputes instantly.

The plan stays with you. Come back after new market data and check you are still on track.