Withdrawal Calculator
Monte Carlo simulation of retirement portfolio withdrawals — 10,000 simulated paths, survival probability, and a safe withdrawal rate table.
Portfolio & Withdrawal Assumptions
Set your portfolio, withdrawal rate, and the return distribution to simulate
Starting value of the portfolio at retirement
Initial withdrawal as a % of portfolio value; grown with inflation each year
Annual rate used to grow the withdrawal amount
Number of years the portfolio needs to last
Baseline Gaussian annual returns — no skew, no fat tails.
Mean annual return assumption
Standard deviation of annual returns
Simulation seed: 156789 — identical inputs always reproduce identical results.
How This Calculator Works
Methodology behind the Monte Carlo withdrawal simulation
Simulation Method
- • 10,000 paths: each simulates one full possible sequence of annual returns over your horizon
- • Withdrawals: taken at the start of each year, then the remaining balance grows (or falls) with that year's simulated return
- • Inflation-adjusted: the withdrawal amount grows with inflation each year, holding purchasing power constant
- • Ruin: once a path's balance hits zero it stays at zero for the rest of the horizon
- • Reproducible: all runs use a fixed random seed (156789), so identical inputs always produce identical results
Return Distributions
- • Normal: Baseline Gaussian annual returns — no skew, no fat tails.
- • Cornish-Fisher: Gaussian returns adjusted by the Cornish-Fisher expansion to carry the given skew and excess kurtosis.
- • Student-t: Fat-tailed returns only, via a Student-t distribution — no skew applied.
- • Jittered: Student-t fat tails with the Cornish-Fisher skew term layered on top — fat tails and skew together.
Survival Probability
The share of the 10,000 simulated paths in which the portfolio never runs out of money before the end of your horizon. Higher is safer — 95%+ is generally considered a very safe withdrawal rate.
Safe Withdrawal Rate Table
Reuses the same simulated return paths to test a range of withdrawal rates, showing the survival probability at each — so you can see how much your withdrawal rate would need to drop to reach a given confidence level.