How Much Do I Need to Retire? FIRE Number Explained
How Much Do I Need to Retire? FIRE Number Explained
The FIRE (Financial Independence, Retire Early) movement has transformed how people think about retirement. Instead of working until 65, FIRE adherents calculate their "number"—the amount needed to never work again—and aggressively save toward it.
But what's your number? And how is it calculated? In this guide, you'll learn the math behind financial independence, understand the famous 4% rule, and calculate your personal FIRE number. Use our calculator to find your retirement target instantly.
Use Our Free FIRE Calculator
Enter your annual expenses and expected returns to calculate your FIRE number. See how long it will take to reach financial independence.
How It Works: The FIRE Number Formula
The 4% Rule:
The FIRE number is based on the Trinity Study's "4% rule": if you withdraw 4% of your portfolio annually, it should last 30+ years with high probability (95%+).
FIRE Number Formula:
FIRE Number = Annual Expenses × 25
This is simply: Annual Expenses / 0.04 = Annual Expenses × 25
Example: If you spend $40,000/year, your FIRE number is $40,000 × 25 = $1,000,000
Variations:
Step-by-Step Example: Calculating Your FIRE Number
Scenario: Sarah earns $100,000/year and wants to know when she can retire.
Step 1: Calculate Annual Expenses
Step 2: Calculate FIRE Number
$46,200 × 25 = $1,155,000
Step 3: Calculate Years to FIRE
Using compound growth formula:
Sarah reaches $1,155,000 in approximately 14 years.
Step 4: Adjust for Variables
Key Factors to Consider
1. The 4% Rule Has Limitations
The 4% rule assumes 30-year retirement (traditional retirement). For 50-year early retirement, consider a more conservative 3-3.5% withdrawal rate. This means multiplying expenses by 28-33 instead of 25.
2. Sequence of Returns Risk
Poor stock returns in your first few retirement years can devastate a portfolio even if average returns are fine. Mitigate with: 2-3 years cash buffer, flexible spending rules, or part-time income initially.
3. Healthcare Is the Wild Card (US)
Without employer insurance, healthcare costs can exceed $20,000/year for a family. Factor this into expenses, or plan to work part-time for benefits until Medicare eligibility at 65.
4. Inflation Erodes Purchasing Power
$40K/year today won't feel the same in 30 years. The 4% rule assumes inflation-adjusted withdrawals (your dollar amount increases with inflation). Make sure your projections account for this.
Frequently Asked Questions
How much money do you need to retire at 50?
For $50,000 annual expenses retiring at 50, you need approximately $1.5M-1.75M (using 3-3.5% withdrawal rate for a 40+ year retirement). Higher expenses or earlier retirement require proportionally more savings.
What is the 4% rule for retirement?
The 4% rule states you can safely withdraw 4% of your portfolio in year one, then adjust for inflation each year after. A $1M portfolio supports $40,000/year. This strategy has historically survived 30+ year retirements 95% of the time.
Can I retire with $1 million?
Yes, if your expenses are under $40,000/year (using 4% rule). $1M supports $40K annual withdrawals. For higher expenses, you'll need more savings or plan to supplement with part-time work.
How much should I save for FIRE?
FIRE adherents typically save 50-70% of income to retire in 10-17 years. At 50% savings rate with 7% returns, you reach FIRE in about 17 years. At 70% savings rate, it's about 8.5 years regardless of income level.
What is Coast FIRE?
Coast FIRE is when you've saved enough that compound growth alone will fund your retirement by traditional age. You can "coast"—stop saving and just cover current expenses with any job. It's a milestone before full FIRE.