Monte Carlo retirement calculator: what it measures

A **Monte Carlo retirement calculator** runs hundreds or thousands of random market paths instead of one average return. You get a distribution of outcomes — median wealth, success rates, and tail risks.

What inputs matter most

Current age and years to retirement
Starting portfolio value and ongoing contributions
Withdrawal spending in retirement
Asset allocation (equity vs bonds drives volatility)

Small changes in spend or retirement age often move success rates more than tweaking expected return by 0.5%.

How to read the output

**Median at retirement** — middle outcome for the growth phase; half the paths are higher, half lower.
**Retirement success %** — share of simulations where the plan funds spending through the horizon.
**Goal funded %** — how current assets compare to a target funded level in the model.

Limits of any calculator

Historical data does not predict the future. Tax law, fees, and behavior (panic selling, dynamic spending) are simplified. Use results for comparison, not certainty.

Run a free snapshot

Quala's retirement calculator runs a growth and decumulation Monte Carlo in seconds — no login required.