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Your odds

Success rate
—
money lasts to the end
Median left at 95
—
the middle outcome
1-in-20 unlucky case
—
5th percentile at 95
If it fails, when?
—
typical age money runs out
Sustainable spending ⓘThe highest annual spending (in today's dollars) that still succeeds in at least 90% of simulations, holding everything else constant.
—
per year at ≥90% success
Withdrawal rate at retirement ⓘFirst-year spending minus guaranteed income, divided by your median savings at retirement. The classic "4% rule" guideline sits around 4%.
—
net of Social Security

How your savings could unfold

Each band shows where your balance falls across all simulated futures, age by age. Half of all paths stay inside the dark band.

Odds your money is still there, age by age

The share of simulations still fully funded at each age — this is where sequence-of-returns risk becomes visible.

What you'd leave behind at 95

Distribution of ending balances across all simulations — the bar at zero is the share of futures where the money ran out.

Checkpoint table

AgeStill fundedUnlucky (5th)MedianLucky (95th)

How this calculator works

Instead of assuming your portfolio earns the same return every single year — the flaw in most retirement calculators — this tool runs thousands of randomized market futures (a technique known as Monte Carlo simulation) and counts how many of them carry your spending all the way to your chosen age. The order of returns matters enormously: two retirements with identical average returns can end completely differently if the bad years hit early, which is called sequence-of-returns risk. Only a simulation can show it.

Each year, your spending and guaranteed income rise with inflation, withdrawals come out at the start of the year (the conservative convention), and the remainder grows at a randomized return calibrated so the long-run average exactly matches your input. Balances can never go below zero, and a plan "fails" the first year it can't cover the gap between spending and guaranteed income. The sustainable spending figure is found by re-running the whole simulation at different spending levels until it lands on the most you can spend with at least 90% success.

The same inputs always produce the same answer: your plan is evaluated against a fixed library of thousands of market futures, so results are fully repeatable and directly comparable when you change one input at a time. (The optional seed in More options swaps in a different fixed library if you want to stress-test your plan further.)

Frequently asked questions

How long will my money last in retirement?
It depends on your withdrawal rate, market luck, and guaranteed income — which is why a single answer is misleading. A useful rule of thumb: at a 4% initial withdrawal rate a diversified portfolio has historically lasted 30+ years in the large majority of cases, while 6%+ fails frequently. Enter your own numbers above to see your specific odds, and check the survival curve to see when the risk concentrates.
What success rate is "good enough"?
Most planners aim for 80–90%+. But 85% doesn't mean a 15% chance of disaster — it means 15% of paths would require an adjustment, like trimming spending for a few years after a bad market. Plans with flexibility can accept lower success rates; plans with rigid spending should aim higher.
What is the 4% rule and is it still valid?
The 4% rule (from the 1994 Bengen study) says you can withdraw 4% of your starting portfolio, adjust it for inflation yearly, and historically survive 30 years. It's a fine starting point, but it ignores Social Security, longer retirements, today's valuations, and your personal flexibility. This calculator effectively rebuilds the rule around your numbers — the "sustainable spending" card is your personal version of it.
What is sequence-of-returns risk?
Losing 30% in your first year of retirement hurts far more than losing 30% in year twenty, because early losses are locked in by the withdrawals you must take while the market is down. Two retirees with identical average returns can end up rich or broke depending purely on the order of good and bad years. It's the single biggest reason retirement outcomes vary so widely — and the main thing this simulation captures that simple calculators can't.
Does this include Social Security and pensions?
Yes — enter your expected benefit in today's dollars and the age it starts. It's treated as inflation-adjusted guaranteed income (like Social Security's cost-of-living adjustments), which directly reduces how much your portfolio must supply each year. Delaying the start age shrinks the early-retirement gap years but raises the benefit you'd enter — try both to compare claiming strategies.
Why plan to age 95? That seems long.
Averages mislead here: life expectancy at 65 is much higher than at birth, and for a 65-year-old couple there's roughly a coin-flip chance that one spouse lives past 92. Running out of money at 90 with years still to live is the failure this tool exists to prevent — planning to 95 (or 100 for the cautious) is the standard recommendation.
Is this financial advice?
No — it's an educational model, and it's only as good as your assumptions. It doesn't know your taxes, account types, healthcare shocks, or ability to adjust. Use it to understand ranges and trade-offs, then pressure-test big decisions with a fiduciary advisor.