Safe Withdrawal Rate Calculator
Test whether your retirement portfolio can sustain your planned withdrawals. Based on the Trinity Study, Bengen's 4% rule, and Monte Carlo simulations using historical stock and bond returns.
Try another scenario
How to Use This Calculator
Will It Last? tab
The default tab. Enter your portfolio value, annual withdrawal, and retirement horizon. The calculator runs 1,000 Monte Carlo simulations using historical stock and bond return distributions to estimate your probability of success. Expand "More options" to adjust stock/bond allocation and inflation settings.
Find Your Rate tab
Use this to find the maximum withdrawal rate for a given success probability. Enter your portfolio, desired success rate (e.g., 90%), and time horizon. The calculator searches for the rate that meets your target and shows a comparison table of common rates (3% through 5%) with their success probabilities.
Dynamic Strategy tab
Compare a fixed withdrawal strategy to dynamic guardrails that adapt to market conditions. Set your base rate, floor rate (for downturns), and ceiling rate (for growth). See how guardrails improve success rates by reducing withdrawals when markets are down and allowing more spending when markets are up.
Share your result
Every input is encoded in the URL. Click Share to send your exact scenario to a spouse, financial advisor, or yourself for later reference.
The Math Behind Safe Withdrawal Rates
Safe withdrawal rate analysis uses historical market returns to test whether a portfolio can sustain a given spending level:
Portfolio[year+1] = (Portfolio[year] − Withdrawal) × (1 + Return)
Success = Portfolio remains > $0 for all years
Success Rate = Successful Simulations ÷ Total Simulations × 100
The calculator uses Monte Carlo simulation with 1,000 runs. Each run generates random annual stock and bond returns drawn from historical distributions (stocks: 10.2% mean, 18% std dev; bonds: 5.3% mean, 6% std dev). This captures the range of outcomes including sequence-of-returns risk — the danger that bad returns early in retirement permanently impair your portfolio.
Unlike simple average-return projections, Monte Carlo simulation reveals the full distribution of outcomes: the best case, worst case, and everything in between. A 90% success rate means your money lasted in 900 out of 1,000 simulated retirement scenarios.
Example
Tom and Maria — newly retired couple, Denver, CO
Tom (65) and Maria (63) have a combined $1.2M in retirement savings (401k + IRA). They plan on 30 years of retirement, want $48,000/yr in withdrawals ($4,000/mo) before Social Security, and have a 60/40 stock/bond allocation. They want to adjust for inflation.
Will It Last? tab
At 4%, Tom and Maria have an 88% chance of their money lasting 30 years with inflation-adjusted withdrawals. The median scenario leaves them with $1.1M, but the worst 10% of scenarios deplete before year 30.
Find Your Rate tab
For 90% confidence, they should withdraw closer to $45,600/yr ($3,800/mo). Once Social Security kicks in at 67-70, they can reduce portfolio withdrawals significantly.
Dynamic Strategy tab
By agreeing to reduce spending to 3.5% during downturns and allowing 4.5% during growth, Tom and Maria boost their success rate from 88% to 96%. The tradeoff is variable income — some years they spend less, some years more.