FIRE number calculator: what you need to retire

What your FIRE number is

Your FIRE number is the amount you need invested to stop working and pay for your life from the portfolio. This FIRE number calculator finds it by taking a year of spending and multiplying it. At a 4% withdrawal rate that multiple is 25. Because money that has to last longer needs a lower withdrawal rate, the multiple here depends on the age you retire.

• Before 45: 31 times a year of spending, a 3.25% withdrawal rate
• 45 to 54: 29 times a year of spending, a 3.45% withdrawal rate
• 55 to 64: 27 times a year of spending, a 3.7% withdrawal rate
• 65 and later: 25 times a year of spending, a 4% withdrawal rate

How to use this FIRE number calculator

Enter your age and the monthly spending you expect in retirement, which is what a month will cost once you stop working, not your income. Then enter what you have invested today and what you add each month. The calculator grows your balance month by month at 6% a year and checks it against the FIRE number for each age. The first age where your balance reaches that number is your answer. It runs in your browser and saves nothing.

A worked example

Say you are 34, spend $4,000 a month, have $120,000 invested and add $1,500 a month. Your balance and the target meet at age 56. At that age the multiple is 27, a 3.7% withdrawal rate, so the FIRE number is $4,000 × 12 × 27 = $1,296,000. The flat 4% rule would say $1,200,000. The extra $96,000 is the cost of a retirement that has to last longer than thirty years.

How to read the result

The calculator shows two numbers: the FIRE number and the age you reach it. They move together. Saving more brings the age down, and a lower age raises the multiple, so the number you are chasing changes as your date does. The same $4,000 a month needs $1,392,000 at 50 and $1,296,000 at 60. If the calculator says “not within 50 years”, your balance does not reach the target in that time at these inputs; lower spending or more invested each month changes that.

Common mistakes

• Using income instead of spending. The number is built on what you spend.
• Counting a home you live in as invested. It does not pay you a withdrawal each year, so the “Invested today” field is for investment accounts.
• Using today's spending when retirement will cost something different. Enter the monthly figure you expect then.
• Leaving out costs the calculator does not add for you. It uses the spending you enter, so include taxes and healthcare in that figure.
• Treating one number as fixed. The FIRE number depends on the age you retire, so it changes when your plan does.

Frequently asked questions

How do you calculate your FIRE number?

Multiply a year of spending by a multiple that depends on the age you retire. At 65 or later the multiple is 25, which is the 4% rule. Earlier retirements use 27, 29 or 31 because the money has to last longer. At $4,000 a month and retirement at 56, the multiple is 27, so the FIRE number is $1,296,000.

What is the 4% rule?

The 4% rule says you can withdraw 4% of your portfolio in the first year of retirement, then adjust that amount for inflation each year. Turned around, it says you need 25 times a year of spending. It was built around a retirement of about thirty years, so this calculator lowers the withdrawal rate for earlier retirements.

Why does my FIRE number change with the age I retire?

A longer retirement needs a lower withdrawal rate, so it needs a bigger multiple of your spending. With the same $4,000 a month, the FIRE number is $1,488,000 at 40, $1,392,000 at 50, $1,296,000 at 60 and $1,200,000 at 65.

Does the FIRE number include Social Security?

No. This calculator leaves Social Security out, so the number is what your own investments would need to cover on their own.

How much do I need to retire at 50?

It depends on what you spend. At $4,000 a month, retiring at 50 takes $1,392,000: $48,000 a year times 29. Change the spending in the calculator to see your own figure.