FIRE Calculator: Find Your Financial Independence Number
Your FIRE number is 25 times your annual expenses — the lump sum that, invested at a 4% withdrawal rate, can fund your lifestyle indefinitely without you ever working again. The FIRE (Financial Independence, Retire Early) movement is built on this math, derived from the 1998 Trinity Study which tested withdrawal rates across historical 30-year market periods. Enter your numbers above to project when your portfolio could cross that threshold.
How it's calculated
The calculator grows your current savings and monthly contributions at your expected annual return until the projected balance equals or exceeds 25 times your annual expenses — your FIRE number. It tells you how many years remain at your current savings rate, and what your balance will be at each target retirement age.
Three FIRE variants use different multiples: lean FIRE targets 20× expenses (a frugal lifestyle, roughly a 5% withdrawal rate); standard FIRE targets 25× (4% rule); and fat FIRE targets 33× or more for a comfortable cushion. The more years your money must last, the lower your safe withdrawal rate should be. For a general retirement projection without an early-exit target, see the retirement savings calculator.
A worked example
Suppose you spend $60,000 per year and want to retire at 45. Your FIRE number is $60,000 × 25 = $1,500,000. You are 30 with $100,000 saved and contribute $2,000 per month. At a 7% annual return, the calculator projects your balance reaches $1,500,000 in roughly 17 years — right at age 47. Bumping contributions by $500 per month closes that gap by about two years. The calculator lets you test these levers instantly.
Common mistakes to avoid
- Using current spending instead of retirement spending. Your FIRE number is based on what you plan to spend in retirement, not necessarily what you spend now — they can differ significantly.
- Ignoring healthcare costs before Medicare eligibility at 65. Private health insurance is often the largest expense for early retirees and can dwarf other budget items.
- Assuming the 4% rule is safe for a 50-year retirement. The Trinity Study modeled 30-year horizons. A 40- or 50-year retirement may need a lower rate, closer to 3.5%, to remain reliable.
- Forgetting taxes on withdrawals. Traditional 401(k) and IRA distributions are taxed as ordinary income, so your after-tax spending power is less than the gross withdrawal.
- Counting on a 100% stock return forever. Sequence-of-returns risk — a market crash in your first retirement years — can permanently damage a portfolio even if long-run returns are good.
Frequently asked questions
What is a FIRE number?
Your FIRE number is 25 times your expected annual expenses in retirement. It represents the portfolio size that, with a 4% annual withdrawal, can fund your lifestyle indefinitely based on historical market data from the Trinity Study. For example, $50,000 in annual spending requires a $1,250,000 FIRE number.
Is the 4% rule safe for early retirement at 40 or 45?
It may not be. The original Trinity Study modeled 30-year retirement periods; retiring at 40 could mean a 50-year horizon. Many FIRE planners use a more conservative 3% to 3.5% withdrawal rate — equivalent to 29× to 33× annual expenses — for very early retirements to reduce failure risk.
What is the difference between lean FIRE, FIRE, and fat FIRE?
Lean FIRE targets roughly 20 times annual expenses and assumes a frugal lifestyle with minimal discretionary spending. Standard FIRE targets 25 times expenses. Fat FIRE targets 33 times or more, providing a large cushion for higher spending or market downturns. Each simply reflects a different withdrawal rate assumption.
How do I access retirement savings before age 59½ without paying the 10% penalty?
Several legal paths exist. The IRS Rule of 72(t) — also called Substantially Equal Periodic Payments (SEPP) under IRS Section 72(t) — lets you take penalty-free IRA withdrawals at any age if you commit to a fixed schedule for five years or until age 59½, whichever is later. A Roth IRA conversion ladder is another common FIRE strategy. See the early retirement calculator for more detail.
Should I include Social Security in my FIRE number calculation?
Yes, but carefully. If you retire at 40, Social Security (SSA) benefits may be decades away and your benefit will be lower because of fewer earning years on record. Use SSA's online estimator for your projected benefit, then treat it as a future income offset that reduces the portfolio withdrawals you need after age 62 or 67.