Safe Withdrawal Rate Calculator
Calculate your sustainable annual retirement withdrawal using the Bengen 4% rule. Adjust portfolio mix, time horizon, and withdrawal rate to see how long your money lasts.
Last updated: 2026-04-19
How Much Can You Safely Withdraw?
The single hardest question in retirement planning: given a portfolio of size X, how much can you spend each year without running out before you run out of years? William Bengen answered this in 1994 with the 4% rule — withdraw 4% of your starting balance, adjust for inflation each year, and you'll survive any 30-year stretch in US history. Three decades later it remains the most-quoted rule in retirement planning, but it has caveats.
How This Calculator Works
The calculator does a deterministic year-by-year projection. Each year it: (1) increases your withdrawal by the inflation rate, (2) subtracts the withdrawal from the portfolio, (3) grows the remaining balance by your portfolio's expected real return. The "Portfolio Lasts" result tells you how many years until depletion under those assumptions. Real returns mean returns net of inflation, so you can compare on equal footing.
Why 4% — and Why Not
Bengen's 4% number assumed a 50/50 stock-bond portfolio over a fixed 30-year horizon, using actual US historical returns including the Great Depression and 1970s stagflation. Subsequent researchers have refined it. Morningstar's annual State of Retirement Income studies have at times argued for ~3.7% given today's lower expected bond returns. Bengen himself has revised upward to 4.5-4.7% with broader diversification. The defensible range for most retirees is 3.5-4.5%, with personal flexibility being the biggest variable.
Beyond the Rule: Guardrails and Variability
The 4% rule is a fixed-dollar strategy — once you start, you increase by inflation regardless of what markets do. That's mathematically safe but emotionally hard. Many planners instead use "guardrails" approaches (Guyton-Klinger, dynamic withdrawal): withdraw more in good years, cut back in bad years. Even small flexibility — taking 10-20% less in down years — substantially raises your sustainable starting rate. The biggest single risk is sequence-of-returns: a bad market in your first 5-10 years of retirement does more damage than the same loss decades later.
Frequently Asked Questions
What is the 4% rule?
The 4% rule comes from financial planner William Bengen's 1994 study. He found that a retiree with a 50/50 stock-bond portfolio could withdraw 4% of their starting balance, adjust that dollar amount for inflation each year, and not run out of money over a 30-year retirement — even through the worst historical periods (the 1929 crash, 1970s stagflation). It's the most widely-used rule of thumb in retirement planning.
Is 4% still safe today?
Recent research has been mixed. Morningstar's annual State of Retirement Income study has at times suggested rates closer to 3.7% given lower expected bond returns and higher equity valuations. Bengen himself has revised his estimate upward to 4.5-4.7% based on broader portfolio diversification. The honest answer: 3.5-4.5% is the defensible range, with personal flexibility (cutting spending in bad years) being the most powerful tool.
What's the difference between SWR and portfolio depletion?
SWR is about safety: the rate at which you would not have run out of money in any historical 30-year window. Portfolio depletion is the simpler question of how long the money lasts at a given withdrawal rate and assumed return. This calculator shows both — your annual withdrawal at the chosen SWR, and a deterministic projection of how long the portfolio lasts.
How does portfolio mix change my SWR?
Counterintuitively, an all-bond portfolio is riskier for sustained withdrawals than a stock-heavy one — bonds don't grow enough to keep up with inflation over 30 years. The classic Bengen sweet spot is 50-75% stocks. Below 30% stocks, sustainable withdrawal rates drop noticeably. Above 75% stocks, sequence-of-returns risk in early retirement becomes the bigger concern.
What is sequence-of-returns risk?
Two retirees with the same average return can have wildly different outcomes if one experiences a big loss in the first few years of retirement. Withdrawing from a depleted portfolio locks in losses. This is why most planners recommend either a higher cash buffer (1-3 years of expenses) or a 'guardrails' strategy — increasing withdrawals after good years and cutting them after bad years — rather than a rigid percentage.