FIRE Calculator: How Much to Retire Early?
Lean FIRE, Regular FIRE, Fat FIRE — the 4% rule demystified. Calculate your number, understand the math, and track your progress in one place.
Financial Independence, Retire Early — FIRE — is not a get-rich-quick scheme. It is a mathematical framework: save and invest aggressively until your portfolio is large enough to fund your lifestyle indefinitely, without ever needing to work again.
The single most common question people ask when they discover FIRE is: how much do I actually need? The answer comes from one simple rule.
The 4% rule — where FIRE numbers come from
The 4% rule originates from the Trinity Study (1998), which analysed US stock market data going back to 1925. The finding: a portfolio invested in a diversified mix of stocks and bonds can sustain a 4% annual withdrawal for at least 30 years with over 95% probability — even through crashes like 1929, 1973, 2000, and 2008.
// FIRE number formula
Annual expenses × 25 = FIRE number
// Because 1 / 0.04 = 25
If you spend $40,000 per year, your FIRE number is $1,000,000. If you spend $60,000, it is $1,500,000. The formula is that direct.
The three types of FIRE
FIRE is not one-size-fits-all. The right version depends on what lifestyle you want in retirement — not just your current spending.
Minimal lifestyle — frugal living, lower-cost location. Works for people who genuinely enjoy a simple life.
Example spend
$30K/yr
FIRE target
$750K
Comfortable middle-class lifestyle. The most common FIRE target. Covers travel, hobbies, and some flexibility.
Example spend
$50K/yr
FIRE target
$1.25M
Generous lifestyle in retirement — business class, dining out often, private school, healthcare buffer.
Example spend
$100K+/yr
FIRE target
$2.5M+
How savings rate determines your timeline
The number that matters more than almost anything else is your savings rate — the percentage of your take-home income you invest each month. Here is why it dominates everything:
| Savings rate | Years to FIRE | Why |
|---|---|---|
| 10% | ~43 years | Traditional retirement timeline |
| 25% | ~32 years | Ahead of average |
| 50% | ~17 years | Realistic early retirement |
| 65% | ~11 years | Aggressive FIRE |
| 75% | ~7 years | Extreme FIRE — needs high income or very low costs |
Assumes 7% average annual real return (inflation-adjusted) on invested assets.
Common mistakes in FIRE planning
Mistake: Using gross income instead of take-home pay
Your savings rate should be calculated on after-tax income. Saving $2K/month on a $5K take-home is a 40% rate, not 24%.
Mistake: Ignoring sequence-of-returns risk
If markets crash in your first few years of retirement, the recovery takes longer. Many FIRE practitioners keep 1–2 years of expenses in cash as a buffer.
Mistake: Forgetting healthcare
For early retirees not yet on government healthcare, private insurance can cost $500–$1,500/month per person. Factor this into your annual expenses.
Mistake: Not tracking net worth monthly
You cannot manage what you do not measure. A monthly net worth snapshot shows you whether your savings rate is actually moving the number.
How to track your FIRE progress
The simplest way to track FIRE progress is to divide your current investable net worth by your FIRE number. If you have $340,000 saved and your target is $1,000,000, you are 34% of the way there.
What you need to watch each month:
- ✓Total investable net worth (exclude primary home for FIRE purposes)
- ✓Monthly savings rate (are you on target?)
- ✓Annual projected expenses in retirement (review this at least yearly)
- ✓Current FIRE percentage and estimated date
For context on where your net worth stands relative to typical milestones by age, see our guide on what is a good net worth at 30, 40, and 50.