Wealth trajectory with Monte Carlo simulation

Simulation
The numbers shown come from a sample profile for illustration – in the calculator you see your own values.

The chart shows your projected wealth trajectory across all FIRE life phases up to age 80 – in today's purchasing power (inflation-adjusted).

The solid line ("Expected trajectory") is the deterministic projection: it assumes you achieve exactly the set real return every year. In the accumulation phase your wealth grows through savings + return. From your FIRE age onwards it declines through withdrawals – the gross withdrawals already include taxes (capital-gains tax, partial exemption, gain share) and health insurance.

The green corridor is the Monte Carlo simulation: 1,000 random paths with fluctuating annual returns. The range of fluctuation (σ) is calculated from your asset allocation (see the glossary entry "Volatility"). The inner corridor (25th–75th percentile) shows the likely range, the outer one (10th–90th percentile) the extreme scenarios. This lets you see how robust your plan is under real market volatility.

The colored background zones mark your FIRE phases: accumulation (green), optionally Coast FIRE (blue) and Barista (orange), withdrawal phase (gray) and pension (blue). Horizontal lines show your FIRE target capital and – if a pension is configured – the reduced capital requirement once your pension starts.

How it is calculated

Wealth(t+1) = wealth(t) × (1 + real return) + cash flow
Real return = nominal return − inflation rate
Cash flow per phase:
Accumulation: +savings rate × 12
Coast: ±0 portfolio cash flow (no saving, no withdrawal – running costs are covered by work income)
Barista: −gross withdrawal (reduced by Barista income)
Withdrawal: −gross withdrawal (incl. capital-gains tax + health insurance)
Pension: −remaining withdrawal (FIRE budget minus statutory pension)

Good to know

Slider values:Return and savings rate in the chart are independent of your saved values – you can play through what-if scenarios without changing your FIRE configuration.
Withdrawals:The withdrawal amounts per phase come from your retirement configuration (budget, tax rate, health-insurance mode, Barista income, pension). The sliders do not change them.