FIRE number calculator for financial independence

What is the FIRE number?

FIRE stands for Financial Independence, Retire Early. Your FIRE number is the total portfolio value at which your investments can sustain your lifestyle indefinitely without you needing to work. It is calculated by dividing your annual expenses by your safe withdrawal rate.

At a 4% withdrawal rate, you need 25 times your annual expenses. At 3.5%, you need about 28.6 times. The years-to-FIRE estimate uses compound growth: it projects your current savings growing at the expected return, plus monthly contributions, until you reach the FIRE number.

Types of FIRE

Lean FIRE

Retire on a frugal budget, typically under $40k/year. Requires a smaller portfolio but leaves little margin for unexpected expenses or lifestyle inflation. Lean FIRE works best for people who genuinely prefer a simple lifestyle and have low fixed costs such as an owned home and no dependents.

FIRE

Retire comfortably with a moderate lifestyle. This is the classic 25x expenses approach at a 4% withdrawal rate. Most FIRE planning assumes a diversified index fund portfolio, low fees, and a retirement horizon of 30 to 40 years.

Fat FIRE

Retire with a generous lifestyle, typically $100k+/year in spending. Requires a larger portfolio but offers more flexibility, security, and the ability to absorb major expenses like private healthcare, children's education, or property without disrupting the retirement plan.

Barista FIRE / Coast FIRE

Hybrid approaches where you stop full-time work before reaching your full FIRE number. In Barista FIRE, part-time or low-stress work covers current living expenses while the portfolio grows to full FIRE. In Coast FIRE, your portfolio is large enough that compound growth alone — with no additional contributions — will reach the FIRE number by a target retirement age. You still need to cover expenses through work, but you no longer need to save.

The 4% rule: origin and limitations

The 4% rule comes from the Trinity Study (Cooley, Hubbard, and Walz, 1998), which analysed historical US stock and bond returns from 1926 to 1995. The study found that a portfolio with a 50/50 stock-to-bond split survived a 4% annual withdrawal over a 30-year period in 95% of historical scenarios. The rule was popularised in FIRE communities as "25x your annual expenses."

Key limitations of the 4% rule:

• It was designed for 30-year retirements, not the 40 to 50-year horizons common in early retirement. Longer time horizons may require a lower withdrawal rate of 3% to 3.5%.
• It is based on US market returns, which have historically been strong. International portfolios or future lower-return environments may perform differently.
• It does not account for flexibility. Most retirees can reduce spending in bad market years, which significantly improves portfolio survival odds compared to rigid fixed-rate withdrawals.
• Sequence of returns risk: poor market returns early in retirement are more damaging than the same average returns distributed more evenly, because early withdrawals reduce the portfolio before it can recover.

How to calculate your FIRE number

FIRE number = annual expenses ÷ safe withdrawal rate

At 4%: FIRE number = annual expenses × 25 At 3.5%: FIRE number = annual expenses × 28.6 At 3%: FIRE number = annual expenses × 33.3

Example: If you spend $60,000 per year, your FIRE number at 4% is $1,500,000. At 3.5%, it is $1,714,286. The difference between a 4% and 3.5% withdrawal rate adds $214,000 to the target — a meaningful increase that can add several years to the accumulation phase.

Years to FIRE

The time to reach your FIRE number depends on three variables: your current savings, your annual contribution rate, and your expected portfolio return. The compound growth formula projects these forward. Higher savings rates dramatically reduce years to FIRE — someone saving 50% of their income typically reaches FIRE in 15 to 17 years from a zero starting point, regardless of their absolute income level.

The savings rate matters more than income because it determines both the accumulation speed (how fast the portfolio grows) and the FIRE number itself (higher savings rate = lower expenses = lower target).

What to include in annual expenses

Include all recurring costs: housing, food, transport, healthcare, insurance, subscriptions, and a reasonable estimate for irregular costs like repairs, travel, and gifts. Many FIRE planners add a 10–20% buffer to their current spending to account for lifestyle changes in retirement and the gradual increase in healthcare costs with age.

Do not include the savings and investment contributions themselves — those disappear at retirement. Do include any costs that currently come from your employer, such as health insurance premiums, that you will need to fund yourself.