FIRE When Can I Retire Calculator: Monte Carlo Odds

3.9%. Morningstar's latest research puts the safe starting withdrawal rate at that figure for a 30-year retirement. "Safe" here means your money is still there in 90% of simulated futures, not just in an average year. Most FIRE "when can I retire" calculators skip that distinction. You type in your savings and spending, the tool assumes one steady return, and it gives you back one tidy date. Real markets don't behave that way, so a single date is less certain than it looks.

So when can you actually retire? Here's the short version. You can retire once your savings can fund your spending across most plausible futures, at a level of confidence you're comfortable with. Below, we cover how to work that out, why the experts' numbers differ, and which risks matter most when a retirement runs for decades.

The short answer: savings, spending, and odds

The usual FIRE shortcut is the rule of 25: save 25 times your annual spending. That's the 4% rule turned around, since 4% of 25× is exactly one year of spending. Calculators from NerdWallet and Boldin use this logic to give you a target, sometimes called your FIRE number.

It's a useful starting point. It isn't an answer. Here's how the target shifts when you use Morningstar's 3.9% instead of a round 4%:

The gap is small on paper. The bigger issue is what these targets assume: a 30-year retirement, spending that rises with inflation and never adjusts, and a 90% success bar. If your plan breaks any of those assumptions, the target needs to move.

How a FIRE when can I retire calculator should work

A typical calculator asks for your age, savings, income or savings rate, spending, and an expected return. It then grows your portfolio at that return until it reaches your FIRE number. The year it gets there is your "retirement date."

The weak spot is that fixed return. If you assume 7% a year, every year, the tool ignores two things that decide whether retirements actually work:

• Volatility. Returns swing. An average of 7% can include several years at -20%.
• Sequence of returns. The order matters. A bad market early in retirement, while you're selling investments to live on, can sink a plan whose long-run average looks fine.

A better FIRE when can I retire calculator replaces that single path with a large number of possible ones.

Monte Carlo, in plain English

A Monte Carlo simulation runs your plan through many randomized market histories. Some include good decades, some bad ones, some a crash in year two. Then it counts how many of those futures end with money left.

The result is a success rate, not a date. "Your money lasts in 870 of 1,000 futures" tells you far more than "you can retire in 2034." It also changes the question to a better one: at what age, and at what spending level, do your odds look good enough?

That's how we built Monte Climb's engine. You enter three numbers: your age, your retirement savings, and your monthly spending. We run them through 1,000 simulated futures and show what share stay funded. It's a probability, not a promise.

Why the experts disagree on a "safe" rate

If you've read about withdrawal rates lately, you've seen several different figures. TheStreet covered how Fidelity, Morningstar, and Bill Bengen land in different places. Here are the main benchmarks:

Sources: Morningstar figures via Financial Advisor and Boldin, Dec 2025. Bengen figures via Advisor Perspectives, Aug 2025.

Three things explain most of the gap:

1. Looking forward vs. looking back. Morningstar builds on its forecasts for future returns. Bengen tests against what actually happened in history. Across roughly 400 historical paths, Bengen found the average sustainable rate was about 7% (Bankrate). That's a good reminder that the "safe" rate is set by the bad years, not the typical ones.
2. Fixed vs. flexible spending. Morningstar says flexibility is worth a lot. Being willing to cut back after a bad year lifted its supported starting rate from 3.9% to 5.7% (Kiplinger).
3. Timing. Morningstar's figure changes every year as valuations and yields change. It was 3.3% in 2021, 3.8% in 2022, 4.0% in 2023, 3.7% in 2024, and 3.9% now.

None of these numbers is wrong. Each one answers a slightly different question, and that's why running your own numbers beats borrowing someone else's.

FIRE retirements run longer than 30 years

Here's a gap most calculators don't address. Every benchmark above assumes a 30-year retirement. If you retire at 45, you may need your money for 45 or 50 years.

We haven't found solid, published safe-rate figures for 40- or 50-year horizons in the research we reviewed. The direction is clear, though: the longer the horizon, the more bad sequences your portfolio has to survive, and the lower the safe starting rate tends to be. A Monte Carlo tool can show this directly. Run the same plan to a later age and watch the success rate move.

Longevity matters at the traditional end too. The Social Security Administration estimates that about one in three 65-year-olds may live to at least 90 (SSA, Retirement Information for Medicare Beneficiaries, 2026). A plan that stops at 85 quietly bets against a third of retirees. Plans built in Monte Climb run to age 95 by default, and you can extend them.

The health care gap calculators ignore

Most FIRE calculators treat health care as just part of "spending." It deserves its own line, for two reasons.

Before 65: the ACA subsidy cliff

If you retire before Medicare, you'll probably buy coverage on the ACA marketplace. The enhanced premium tax credits expired, and the subsidy cliff came back on January 1, 2026. If your income goes above 400% of the federal poverty level, the credit disappears entirely (Mezzi, Financial Planning).

Which account you withdraw from matters. Traditional account withdrawals, capital gains, and Roth conversions count toward that income test. Roth withdrawals generally don't (Q3 Advisors). Two people with the same savings can end up with very different premiums. If you're considering an early retirement, look closely at these bridge years.

After 65: Medicare isn't free

Fidelity's 2025 estimate is that a 65-year-old retiring this year will spend $172,500 on Medicare premiums, deductibles, and prescriptions over retirement. That figure doesn't include long-term care (Fidelity Investments, 2025 Retiree Health Care Cost Estimate, Jul 2025). That's a major line item, not a rounding error. Our engine charges Medicare premiums and income-based surcharges year by year instead of using one flat guess.

How to find your realistic retirement age

You don't need a perfect model to start. You need a first estimate. Only 52% of workers have estimated the monthly income they'll need in retirement, so the other 48% are guessing (EBRI/Greenwald, Retirement Confidence Survey 2025).

A simple process:

1. Get your monthly spending right. This input moves the result more than any return assumption. Use actual numbers, not a hoped-for budget.
2. Check your success rate today. Enter your age, savings, and spending. See how many futures stay funded.
3. Change one thing at a time. Try lower spending, a later age, or more savings, and see which change helps your odds most.
4. Pick your confidence bar. Morningstar uses 90%. Some people accept less because they're willing to cut spending. Others want more.
5. Plan for flexibility. If you'd cut back after a bad year, you can likely support a higher starting rate than a fixed-spending plan suggests.
6. Pressure-test the hard parts. Think through health care before 65, a longer life than average, and early market losses.

If you'd rather talk it through, William, our AI planner, handles questions like "Am I on track?", "Can I retire at 62?", and "What's a sustainable spend?" Ask him the way you'd ask a friend.

One caveat: this is planning software, not advice. A success rate helps you make decisions. It isn't a guarantee.

Run your own numbers

Three numbers. 1,000 futures. One clear answer about whether your money lasts. It runs in your browser, and nothing is saved until you say so.

Show my answer →

Want to go further? You can try the full Monte Climb retirement planning app for $1 for 7 days and build a plan that runs to 95 or beyond.

Frequently asked questions

How do I calculate when I can retire with FIRE?

Start with the rule of 25: multiply your annual spending by 25 to get a target, which is the 4% rule turned around. For a more realistic answer, run your savings and spending through a Monte Carlo simulation. It shows the share of possible market futures in which your money lasts, so you can find the age and spending level where your odds look acceptable.

Is the 4% rule still safe in 2026?

It depends on the benchmark. Morningstar's latest research puts the safe starting rate at 3.9% for a 30-year retirement with fixed, inflation-adjusted spending and a 90% success target. Bill Bengen's updated historical work supports 4.7%. Morningstar also found that flexible spending supported 5.7%.

What safe withdrawal rate should I use for early retirement?

The major benchmarks assume a 30-year retirement, and an early retiree may need 40 to 50 years. Published figures for those longer horizons are scarce. The general direction is that a longer horizon calls for a lower starting rate, so it helps to test your own plan to a later end age and see how the success rate changes.

What is a Monte Carlo retirement calculator?

It runs your plan through many randomized market scenarios instead of one average return. It then reports how many of those futures end with money left. Monte Climb, for example, uses 1,000 simulated futures and shows the result as a success rate: a probability, not a promise.

How does health care affect my FIRE retirement date?

Before 65, the ACA subsidy cliff came back on January 1, 2026. If your income goes above 400% of the federal poverty level, the premium credit disappears entirely. After 65, Fidelity estimates a 65-year-old retiring in 2025 will spend $172,500 on Medicare costs over retirement, not counting long-term care.