# 4% Rule Calculator

> See the chance your retirement savings last under the 4% rule, how long they last at a steady return, and the rate that holds up in 9 of 10 markets.

Source: https://mycoastfire.com/4-percent-rule-calculator
Last updated: 2026-09-24

Enter your portfolio and yearly spending to see how often the money lasts across 2,000 simulated markets, and the highest starting rate that survives 9 out of 10.

## What does the 4% rule actually say?

It says that if you withdraw 4% of your portfolio in your first year of retirement, then raise that dollar amount by inflation every year after, your money should last at least 30 years. On $1.5 million that’s $60,000 in year one, maybe $61,800 the next if prices rose 3%, and so on, regardless of what the market does.

The rule comes from a 1994 paper by financial planner [William Bengen in the Journal of Financial Planning](https://www.financialplanningassociation.org/sites/default/files/2021-04/MAR04%20Determining%20Withdrawal%20Rates%20Using%20Historical%20Data.pdf). He took a portfolio of half US stocks and half intermediate-term Treasuries, kept it rebalanced, and replayed actual US returns and inflation for retirements starting in each year from 1926 to 1976. At a 4% first-year withdrawal, no starting year ran out of money in fewer than 33 years. At 4.25%, one could run dry in 28.

Four years later, three Trinity University finance professors ran a similar test in the [AAII Journal](https://www.aaii.com/journal/199802/feature.pdf), now known as the Trinity Study. They used the S&P 500 and long-term, high-grade corporate bonds from 1926 to 1995, and counted a retirement as a success if the portfolio never hit zero. With inflation-adjusted withdrawals of 4% over 30 years, a 50/50 portfolio survived 95% of the 41 periods they tested, and a 75/25 portfolio survived 98%. The study left out taxes and transaction costs.

## How this calculator works

Instead of replaying history, it builds 2,000 possible markets and counts how many of them your plan survives.

```
withdrawal rate = first-year spending ÷ portfolio
real return     = (1 + expected return) ÷ (1 + inflation) − 1

For each of 2,000 paths, for each year of retirement:
  if balance < spending, the path has run out
  balance = (balance − spending) × exp( ln(1 + real return) + volatility × Z )    Z is a fresh standard normal draw

chance the money lasts = share of paths that pay every year's spending in full
```

Everything is in today’s dollars, so your spending stays flat on paper, which is the same as raising it with inflation in real life. Each year’s return is drawn at random from a lognormal distribution whose median is your real return, the same model our [Monte Carlo Coast FIRE calculator](https://mycoastfire.com/coast-fire-monte-carlo-calculator) uses. The spending comes out at the start of each year, slightly more cautious than Bengen’s end-of-year withdrawals.

“Lasts at a steady return” ignores the randomness and gives every year the same real return, to show how long the money would last if markets were perfectly smooth. The last figure is the highest starting withdrawal rate that pays out in full in at least 1,800 of the 2,000 markets. It’s found by testing rates against one fixed set of markets, so it doesn’t move when you change your spending. The [methodology page](https://mycoastfire.com/methodology) covers the assumptions shared by all our calculators.

## A worked example

Lena is 52, has $1.5 million invested and expects to spend $60,000 a year, a 4% withdrawal rate. With the calculator’s defaults (7% return, 3% inflation, 15% volatility), here’s how often her money lasts, depending on how long retirement runs and what rate she starts at:

| Years in retirement | 4% ($60,000) | 3.5% ($52,500) | 3.25% ($48,750) | Rate that lasts in 9 of 10 |
| --- | --- | --- | --- | --- |
| 30 | 75% | 83% | 87% | 3.06% |
| 40 | 61% | 70% | 75% | 2.40% |
| 50 | 53% | 63% | 68% | 2.18% |

At a perfectly steady 3.9% real return, $60,000 a year would last Lena 71 years. The simulation is less kind: over 30 years, a 4% start lasts in 75% of markets, and her typical path still ends with about $1,180,000. The failures come from paths where the first decade goes badly, which is what people mean by sequence risk. A crash in year two does far more damage than the same crash in year twenty, because you’re selling shares at low prices to pay the bills while the balance is still large.

The bigger lesson is in the rows. Going from 30 to 50 years costs more than cutting from 4% to 3.25% buys back. Lena is 52, so a 40-year retirement only takes her to 92. That row, not the 30-year one, is the one she should plan around.

## Why are these odds lower than the Trinity Study’s?

Mostly because of the defaults. A 7% return with 3% inflation is a real return of about 3.9%, and 15% volatility is what you’d expect from a mostly-stock portfolio. That’s a lower return and a bumpier ride than what a balanced US portfolio actually got in the 20th century. Bengen’s own figures had stocks compounding at 10.3% and intermediate Treasuries at 5.1% from 1926, with inflation around 3%, which works out to about 8.2% a year for a 60/40 mix.

Put those numbers in (8.2% return, 3% inflation, 10% volatility) and a 4% withdrawal lasts 30 years in 93% of simulated markets, close to what the Trinity Study found. Keep the 7% return and only lower volatility to 10%, and it’s 85%.

The model also treats every year as independent of the one before. Real markets aren’t like that, and a random draw can string together runs of bad years in ways the US record hasn’t. The historical studies have the opposite problem: they’re built on about 40 overlapping 30-year windows from one country’s very good century, which is a small sample to bet a retirement on.

I don’t think either approach is right on its own. The backtests tell you what has worked. The simulation tells you what happens if the future is flatter than the past, and with cautious inputs it’s a useful stress test.

## What withdrawal rate should an early retiree use?

Something below 4%, in most cases. The original studies stopped at 30 years, and the Trinity authors themselves concluded that early retirees expecting long payout periods should plan on lower rates. If you [retire at 50](https://mycoastfire.com/retire-at-50), your money might have to last 45 years.

The most thorough public work on this is Karsten Jeske’s [safe withdrawal rate series](https://earlyretirementnow.com/safe-withdrawal-rate-series/) at Early Retirement Now, which tests 60-year retirements against US data going back to 1871. In [part one](https://earlyretirementnow.com/2016/12/07/the-ultimate-guide-to-safe-withdrawal-rates-part-1-intro/) he found that a 4% rate with a 50/50 portfolio succeeded about 95% of the time over 30 years but only about 65% over 60 years. His conclusion for early retirees is a rate in the 3.25% to 3.5% range, and he leans toward the low end when stocks are expensive relative to earnings.

Bengen went the other way for traditional retirees. His 2025 book, A Richer Retirement, puts the worst-case safe rate at 4.7% for 30 years, using a more diversified portfolio that adds small-company and international stocks. Both can be true at once. More asset classes raise the number, and a longer horizon lowers it.

If I were retiring at 50, I’d plan on 3.5% and treat anything above that as income I’d have to earn by being willing to cut back in a bad decade.

## How does the 4% rule connect to Coast FIRE?

Your FIRE number is your yearly spending divided by your withdrawal rate. That number then drives everything else: your [FIRE date](https://mycoastfire.com/fire-calculator), and your [Coast FIRE number](https://mycoastfire.com/), the amount that grows into your FIRE number with no more contributions. For $60,000 of spending and 30 years to go at a 3.9% real return:

| Withdrawal rate | FIRE number | Coast FIRE number, 30 years out |
| --- | --- | --- |
| 4% | $1,500,000 | $478,294 |
| 3.5% | $1,714,286 | $546,621 |
| 3.25% | $1,846,154 | $588,669 |

Dropping from 4% to 3.25% raises both numbers by about 23%. That’s a real cost, and it’s why I’d pick the withdrawal rate first, based on how long your retirement could last, before trusting any Coast FIRE date.

Try a lower withdrawal rate

Change the withdrawal rate under Assumptions and see how much later your FIRE date moves.

[Open the FIRE calculator](https://mycoastfire.com/fire-calculator)

## What this calculator leaves out

It doesn’t replay history, so you won’t see what retiring in 1929 or 1966 would have done to you. For that, the backtests above are the better guide.

There are no fees or taxes. Subtract fund fees from your expected return, and include the taxes you’ll owe on withdrawals in your spending.

Spending is fixed. In real life you’d probably cut back after a bad year, and plenty of people spend less in their 80s than in their 60s. The simulation assumes you never adjust, so treat it as a worst case for behavior.

Social Security and pensions aren’t included. If a benefit will cover part of your spending from 67, your portfolio only has to carry the whole load until then. [This post on Social Security and Coast FIRE](https://mycoastfire.com/blog/coast-fire-with-social-security) walks through that bridge.

Finally, inflation is a fixed number here. A burst of high inflation early in retirement was what hurt Bengen’s worst historical cases most, and this model can’t produce one.

## Questions people ask

### Does the 4% rule mean I take 4% of my balance every year?

No. You take 4% of your starting balance in the first year, then raise that dollar amount with inflation every year, whatever the market does. Taking 4% of whatever the balance happens to be is a different strategy. It can't run out, but your income rises and falls with the market.

### Is the 4% rule still safe?

For a 30-year retirement with a mix of stocks and bonds, it held up in nearly every starting year the original studies tested, including the Depression and the 1970s. It's much thinner for 40 or 50 years, and it assumes you never trim spending after a bad year. I'd treat it as a sensible starting point for someone retiring in their 60s, not a guarantee.

### What withdrawal rate should I use if I retire at 45 or 50?

Something lower than 4%. Research aimed at early retirees, like Karsten Jeske's safe withdrawal rate series, tends to land around 3.25% to 3.5% for retirements of up to 60 years. Set the years in retirement to your own horizon and watch how much the odds move.

### Does this calculator count Social Security?

No. It assumes the portfolio pays for everything. If a benefit or pension will cover part of your spending later, the portfolio needs less, but only from the year that income starts. Our post on Coast FIRE with Social Security shows how to account for that gap.

## Keep reading

-   [FIRE calculatorYour FIRE number and the age you get there.](https://mycoastfire.com/fire-calculator)
-   [Coast FIRE Monte CarloThe same kind of simulation, for the years before you retire.](https://mycoastfire.com/coast-fire-monte-carlo-calculator)
-   [MethodologyEvery assumption behind our calculators.](https://mycoastfire.com/methodology)