Can I Retire? Here's How to Actually Know.
The 25×-your-spending rule of thumb isn't wrong. It's just not an answer — it's a starting point that skips every variable that actually decides your outcome.
- "25× your annual spending" is a useful floor, not a real answer — it assumes a fixed 30-year retirement, a static withdrawal rate, and ignores Social Security timing, taxes, and how long you'll actually live.
- The honest answer is a probability, not a yes or no: what percentage of simulated market futures does your specific plan survive? Above 85% is generally solid; below 65% usually means real changes are needed.
- You can run this on your own numbers below — free, no signup, nothing leaves your browser.
The rule of thumb, and where it breaks
"Multiply your annual spending by 25" is the retirement-planning equivalent of a BMI chart — a fast, useful first pass that gets treated as a diagnosis. It comes from the same place as the 4% rule: a study of historical 30-year retirement windows that found a portfolio withdrawing 4% annually, adjusted for inflation, survived almost all of them. Invert that math and you get 25×.
The problem isn't that the math is wrong. It's that it was built for one shape of retirement — a fixed 30-year horizon, a static withdrawal rate, no Social Security in the picture, no tax drag, no flexibility in spending — and gets applied to retirements that look nothing like that. A 45-year-old planning a 45-year retirement is using a 30-year tool. Someone claiming Social Security at 70 instead of 62 is sitting on a benefit that can cover a third or more of their spending, un-modeled. Someone who can cut discretionary spending 15% in a bad market has more room than the static math gives them credit for.
None of that makes 25× useless. It makes it a floor — a number to sanity-check against, not a number to retire on.
What actually determines the answer
Five things do almost all of the work, and a real calculation has to account for all five at once, not one at a time:
- What you actually spend — not a guess, not last year's budget rounded up. Most people underestimate this by a meaningful margin until they track it.
- What you have saved, and where — taxable, tax-deferred, and Roth balances all get taxed differently on the way out, which changes how far the same dollar goes.
- Social Security — amount and claiming age. Claiming at 62 permanently cuts the benefit by roughly 30% versus full retirement age; waiting until 70 increases it by about 24% above that. For many households this is the single biggest lever in the whole plan.
- How long the money needs to last. Not a guess at "life expectancy" — the honest version plans toward the tail of the distribution, not the coin-flip average, especially for a couple where one spouse likely outlives the other.
- Market variance, not just average return. A 7% average annual return is compatible with wildly different outcomes depending on when the bad years land — which is the part a spreadsheet average can't show you and a simulation can.
Change any one of these and the answer moves. A rule of thumb can only look at one number at a time. A real plan has to look at all five together.
Why the honest answer is a probability
Ask "can I retire?" and expect a yes or no, and you're asking the wrong question. Markets don't produce one future — they produce a distribution of possible futures, and your plan survives some of them and doesn't survive others. The useful number isn't "yes" or "no." It's: out of many simulated market paths, applied to your real spending, savings, and Social Security timing, what fraction leaves you with money at the end?
That's what a Monte Carlo simulation does — it runs your plan through hundreds or thousands of randomized market sequences (not one average, many different orderings of good years and bad years) and reports the survival rate. As a rough guide: above 85% is generally considered solid ground. Below 65% usually means real changes are needed — a later retirement age, higher savings, or lower planned spending. The 65–85% range is a gray zone where smaller moves, like working one more year or trimming discretionary spending, can often close the gap.
A 100% success rate isn't a guarantee, either — it means the plan survived every scenario the model tested, which is strong evidence, not certainty. No simulation can price in a tax law that doesn't exist yet or a health event with no historical precedent. Treat the number as the best honest estimate available, not a promise.
A worked example
Take someone 52 years old with $850,000 saved, contributing $30,000 a year, planning to spend $5,500 a month in retirement, expecting $2,400/month from Social Security at full retirement age. Run the 25×-spending shortcut and the target looks like $1.65M — a number that, on its own, says "not yet."
Run the same numbers through a simulation that accounts for Social Security timing, tax-aware withdrawal order, and market variance, and the picture changes:
| Retirement age | Success rate | Read |
|---|---|---|
| 58 | 61% | Below the comfort line — real risk |
| 61 | 79% | Gray zone — workable with a few adjustments |
| 63 | 91% | Solid ground |
The rule of thumb said "not yet" without saying how far off. The simulation says exactly how much runway closes the gap — in this case, roughly five years, not an indefinite "keep saving and hope." That specificity is the entire value of running the real math instead of a shortcut.
What this doesn't capture
Even a full simulation has honest limits, and pretending otherwise would be the same sin as the rule of thumb it's replacing. It can't predict a specific future market crash, a specific tax law change, or a specific health event — it prices in the range of what's historically plausible, not what will actually happen. It's a projection, not a prediction. Treat a strong success rate as a green light to keep planning with confidence, not as a signed guarantee.
How this is calculated
The number above comes from a 1,000-scenario Monte Carlo simulation using randomized market returns based on historical data, accounting for inflation, Social Security timing, tax treatment across account types, and withdrawal sequencing. It's the same engine behind the full app — free to run, no account required. The complete math, including the specific assumptions and data sources, is documented in the methodology.
Common questions
This article runs one calculator on default numbers. The full app models your complete plan — taxes, Social Security optimization, and stress-testing against real market history.
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