Will My Money Last? — Retirement Survival Stress-Test

Because the future is not one path — it is thousands of possible paths, and a single average return hides the risk that matters most. A flat 5%-every-year projection will always tell you the same tidy story, but real markets deliver 5% as a jagged sequence of good and bad years, and the ORDER of those years changes everything once you start withdrawing. So this tool runs 1,000 simulated lifetimes, each a different plausible order of returns drawn from your expected return and volatility, and reports the share in which your money outlasts you. A survival probability is an honest answer to an uncertain question: instead of "you will have $412,000 left" (which will almost never be exactly true), it says "your plan works in 94% of futures like yours."

Sequence-of-returns risk is the danger that a market crash early in retirement does far more damage than the same crash later. While you are working, a crash is almost a gift — you buy cheap. But once you are withdrawing, a crash forces you to sell more shares to cover the same spending, and those sold shares can never recover. Two retirees with the identical average return over 30 years can end up in completely different places: the one who hit a bad decade first may run dry, while the one who got the bad decade last dies with millions. Average return tells you nothing about this; only a simulation that varies the order — like this one — can surface it. It is the single most underappreciated risk in retirement planning.

It is fully reproducible. Although it runs 1,000 randomized market lifetimes, the randomness comes from a fixed seed that is reset at the start of every run, so the same inputs always produce the exact same survival probability — every refresh, on every device, forever. This is deliberate. A calculator whose headline number flickers between 84% and 87% each time you reload erodes trust and makes it impossible to compare scenarios cleanly. Here, when you change one input and survival moves, you know it moved because of your change, not because of random noise. It also means the worked example on this page and the calculator you run agree to the exact percentage point.

Because they attack the problem from more than one side at once. Saving an extra $100,000 helps, but it is a single lever. Working three more years is a triple lever: you add three more years of contributions, you give the whole portfolio three more years to compound before you touch it, AND you cut three years of withdrawals off the far end. Cutting spending is a permanent double lever: every dollar you do not spend is a dollar you do not have to withdraw for the rest of your life, which lowers the bar the portfolio must clear in every single simulated year. That is why, on the Lever Board, these moves so often buy more survival points than a lump-sum windfall. The most durable fixes change the shape of the plan, not just its starting balance.

For most people, 85% to 95% is the sensible target zone. Below about 75%, the plan is fragile — a bad early decade has a real chance of sinking it, and you should tighten something. But chasing 100% is usually a mistake, not a triumph: a 100% survival probability across every simulated crash typically means you are dramatically over-saving and under-living, dying with a fortune you denied yourself. A plan that survives 90% of futures and lets you actually enjoy your money is almost always better than one that survives 100% because you spent your retirement being needlessly frugal. Aim for high confidence, keep a cash buffer for the bad early years, and stay flexible — a willingness to trim spending in a down market is worth several percentage points of survival on its own.

Use REAL return here — growth after inflation — because spending is entered in today’s dollars and the whole simulation runs in today’s purchasing power. If you expect 8% nominal and 3% inflation, enter about 5% real. A diversified stock/bond portfolio has historically delivered roughly 4–6% real over long periods after realistic fees. For volatility (the standard deviation of annual returns), use about 18% for an all-stock portfolio, about 11% for a balanced 60/40 mix, and about 7% for a conservative, bond-heavy allocation. Higher volatility widens the range of outcomes and, all else equal, lowers survival — which is exactly why a retiree often shifts toward the lower-volatility end. Inflation data comes from the BLS Consumer Price Index; long-run return and volatility figures are well documented in the Bogleheads safe-withdrawal-rate research linked below.