FIRE Number Calculator

Your FIRE number is the size of portfolio that can fund your annual spending for the rest of your life. It is annual spending divided by a withdrawal rate: at 4%, 25 times what you spend; at 3.5%, about 28.6 times. The tool shows it at five rates, from cautious to aggressive, so you can see how much the choice matters.

The 4% figure comes from US research on 30-year retirements, Bengen's 1994 study and the 1998 Trinity study. An early retirement may need to last 40 or 50 years, which points to a lower rate. Flexibility points the other way: a plan that can trim spending in bad years can usually start higher. Neither country's government pensions are counted in the multiple.

At the tool's starting spend of $70,000 a year, the FIRE number ranges from $1.4 million at 5.0% to $2.33 million at 3.0%. At the common 4% it is $1,750,000, and at 3.5% it is $2,000,000.

The spread between the most and least cautious rate is $933,000, which at a typical savings rate is several years of work. That is why the withdrawal rate deserves as much thought as the spending figure, and why it is worth testing in a simulation rather than picking one by habit.

If a government pension will pay part of your spending later, the Age Pension from 67 in Australia or Social Security from 62 to 70 in the US, the portfolio does not have to fund that part for life. But it still has to fund everything until the pension starts, and in Australia the Age Pension is means-tested, so a large portfolio may receive little or none at first.

A single multiple cannot capture that shape, which is why the country calculators let you add a pension from the age it starts and work through the plan year by year.

Because the FIRE number is a multiple of spending, every $1,000 a year of spending adds $25,000 to it at 4%. Building retirement spending from what you actually spend now, adjusted for what will change, such as a mortgage ending or children leaving home, gives a far better number than a rule of thumb about income.

Include the tax you expect to pay on withdrawals, and irregular costs like car replacement and home repairs averaged over the years.

Three Australian rules change what the number means. Super is preserved until 60, so if you retire earlier, enough of the number has to sit outside super to cover the years until then. Tax in retirement is usually low, because super pensions from 60 are tax free. And from 67, a means-tested Age Pension can take over part of the spending. The Australian FIRE calculator models the bridge to 60 and the tax on super.

In the US, 401(k) and IRA money generally carries a 10% additional tax before 59½, so an early retiree needs enough in a brokerage account or another reachable source for the years before then. Health insurance until Medicare at 65 is often a large line in the budget, and Social Security later reduces what the portfolio has to provide. The US FIRE calculator models the bridge to 59½.

A FIRE number is a target, not a plan. It does not tell you when you will reach it, whether the money in your accounts is reachable when you need it, or how the plan fares in a bad run of markets. The full calculators answer those: the Australian FIRE calculator and US FIRE calculator find your earliest retirement age, and the drawdown simulators test the withdrawal rate against thousands of market paths.