About
Monte Carlo runs many simulated retirements with randomized annual returns (sampled from normal distribution). 80%+ success = solid plan. Sequence of returns risk: bad early years dramatically hurt outcomes. Reduce withdrawal in downturns to boost success rate.
Typical 2026 success-rate benchmarks for a 30-year retirement with a 60/40 portfolio: a 4.0% initial withdrawal lands near 90 to 94% success in 10,000-trial simulations; 4.5% drops to roughly 80%; 5.0% slips to 65 to 70%. For a 40-year horizon (early retirees), shave 0.3 to 0.5 percentage points off the starting rate to keep success above 85%. Vanguard, Morningstar, and the Trinity update papers all converge in this range, though normal-distribution Monte Carlo understates tail risk because real markets show fatter tails than the bell curve.
Common pitfalls
- Confusing 95% success with safety. A 5% failure rate over 30 years is still one in twenty retirees running out of money. Pair the headline number with a guardrail rule that cuts spending in down years.
- Ignoring lifestyle inflation. Simulators inflate the withdrawal at CPI, but healthcare inflation is 2-3 points higher and tends to bite late in retirement when reserves are smallest.
Formula
Frequently asked questions
How accurate is the Monte Carlo Retirement?
It applies the standard formula. Accuracy is limited only by your input precision. For decisions with material consequences (taxes, medical, legal, structural), use the result as a starting point and verify with a qualified professional in the relevant field.
Is the Monte Carlo Retirement free to use?
Yes. 100% free, no signup, no payment, no API key. The site is funded by display ads around the tool but not inside the calculation flow.
Are my inputs saved anywhere?
No. All inputs stay in your browser tab. Closing the tab discards them. The site uses Google Analytics for traffic measurement (anonymized) but the analytics never see what you type into the form.
Can I use the Monte Carlo Retirement on my phone?
Yes. The tool is responsive and tested on iOS Safari, Android Chrome, and major desktop browsers. Touch targets meet Apple's 44pt and Google's 48dp minimum.
Does the Monte Carlo Retirement work offline?
Yes. Once the page has loaded, it works without internet. The calculation runs in JavaScript on your device.
How do I report a bug or suggest improvement to the Monte Carlo Retirement?
Email hi@3tej.com with the URL of this page and a description of what you saw vs expected. We typically respond within 72 hours.
Can I share results from the Monte Carlo Retirement?
Take a screenshot or copy the output. The page doesn't generate shareable URLs for specific calculations - inputs stay in your browser only.
Why are the results different from another monte carlo retirement tool?
Most likely: different formula assumptions, different default values, different rounding rules, or different applicable rates. Check the methodology if both tools document it. Both can be valid for different scenarios.
Is the Monte Carlo Retirement accurate?
The Monte Carlo Retirement applies the standard formula for monte carlo retirement. Accuracy is limited only by your input precision. For decisions with material consequences, use the result as a starting point and verify with a qualified professional or the relevant official source.
Is the Monte Carlo Retirement free?
Yes. 100% free, no signup, no payment, no API key. The site is funded by display ads that appear around the tool but not inside the calculation flow.
Are my inputs saved?
No. Inputs stay in your browser tab. Closing the tab discards them. The site uses Google Analytics for traffic measurement (anonymized) but does not see what you type into the form.
How to use the Monte Carlo Retirement
The Monte Carlo Retirement is a browser-based tool that runs entirely on your device. Inputs you enter never reach a server - all calculations happen client-side in JavaScript. This means:
- Privacy: nothing is logged, sent, or stored by 3Tej. Inputs disappear when you close the tab.
- Speed: results update as you type. No network round trip.
- Offline use: once the page is cached, it works without internet.
- No signup: no account, no email, no rate limits.
Step by step
- Enter your inputs in the form above. Each field is labeled with its unit (currency, percent, kg, etc.) and the expected range.
- Read the result as it updates. The number reflects the formula commonly accepted in Monte Carlo Retirement-related calculations.
- Adjust to see sensitivity: change one input at a time and watch how the output moves. This is the fastest way to understand which variable matters most.
- Copy or screenshot the result for later reference. The page state persists for the session if your browser allows it.
When you would use this
- Quick estimates: when you need a number now and don't want to open a spreadsheet.
- Sensitivity analysis: testing how a result changes as inputs vary, before committing to a real-world decision.
- Comparison: running the same calculation with different inputs to compare options side by side.
- Learning: building intuition for how the underlying math behaves.
- Documentation: capturing a snapshot of inputs and outputs at a point in time.