FIRE Number Calculator: How to Calculate Your Financial Independence Number

What Is a FIRE Number?

Your FIRE number (Financial Independence, Retire Early number) is the total amount of invested wealth you need to cover your living expenses forever — without working. Once you reach this number, work becomes optional. Your investments generate enough passive income to fund your life.

We call it your Quit Number because that's what it really means: the number at which you can quit.

The Formula

The FIRE number formula is simple:

FIRE Number = Annual Expenses × 25

If you spend $50,000 per year, your FIRE number is $1,250,000. If you spend $40,000, it's $1,000,000. If you spend $70,000, it's $1,750,000.

The formula works for everyone because it's based on your expenses, not your income. A teacher spending $35,000 per year has a lower FIRE number ($875,000) than a software engineer spending $100,000 per year ($2,500,000).

Why 25x Works

The 25x multiplier comes from the 4% safe withdrawal rate. If you withdraw 4% of your portfolio each year, the math works out to 1 ÷ 0.04 = 25.

Historical data backs this up. Since 1926, a diversified portfolio of stocks and bonds has survived a 4% annual withdrawal rate through every 30-year period in U.S. market history — including the Great Depression, the 1970s stagflation, the dot-com crash, and the 2008 financial crisis.

For early retirees planning 40-50+ year retirements, some researchers recommend a 3.5% rate (roughly 29x expenses) for extra safety. The latest research on withdrawal rates shows that adding flexibility to your spending makes even 4% very safe over long timeframes.

Step-by-Step Calculation

Step 1: Find your monthly expenses

Pull your last 3-6 months of bank and credit card statements. Add everything up: housing, food, transportation, insurance, utilities, subscriptions, entertainment, everything. Divide by the number of months for your average.

Don't forget irregular expenses: car maintenance, holiday gifts, annual subscriptions, home repairs. These add 5-15% to most people's monthly average.

Step 2: Adjust for early retirement

Remove expenses that disappear when you stop working: commuting costs, professional wardrobe, work lunches, payroll taxes. Add expenses that increase: health insurance (if losing employer coverage), potentially more travel or hobby spending.

Step 3: Annualize it

Multiply your adjusted monthly expenses by 12 to get your annual number.

Step 4: Multiply by 25

This is your FIRE number. The amount you need invested — not including your home equity or other non-liquid assets — to retire.

Example

Monthly expenses: $4,500. Remove $400 in work costs, add $350 for health insurance. Adjusted: $4,450/month. Annual: $53,400. FIRE number: $53,400 × 25 = $1,335,000.

What Most FIRE Calculators Get Wrong

Many FIRE calculators make the process more complicated than it needs to be — or oversimplify in the wrong ways.

Too many inputs

Some calculators ask for 20+ data points: expected Social Security, pension details, state tax rates, asset allocation, inflation assumptions. These are useful for fine-tuning, but they paralyze beginners. You don't need precision to the dollar. You need a target to aim at.

Ignoring the emotional component

A FIRE number isn't just math — it's motivation. Knowing you need $1.2 million and you're 35% of the way there (your Quit Score) creates urgency and direction that a probability distribution never will. Most calculators give you a number. They don't give you progress.

No timeline

Knowing your FIRE number is step one. Knowing when you'll reach it — your Quit Date — is what actually changes behavior. The best FIRE calculators show you both: your target and your projected arrival date.

FIRE Number vs. Quit Number

Your FIRE number and your Quit Number are the same thing calculated the same way. We use "Quit Number" because it captures what the number actually means: the point at which you can quit your job and live on your investments.

"Financial Independence Number" is accurate but abstract. "Quit Number" is concrete. It connects the math to the outcome — walking out of work on your terms.

What Counts Toward Your Number

Your FIRE number represents invested assets that generate returns. This includes:

• Retirement accounts: 401(k), IRA, Roth IRA, 403(b), TSP
• Taxable brokerage accounts: Individual or joint investment accounts
• HSA balance: If invested (not just in cash)

This typically does not include:

• Home equity: Unless you plan to sell or downsize
• Cash savings: Emergency fund or checking/savings beyond a 1-2 year buffer
• Business value: Unless you plan to sell
• Cars, possessions: Depreciating assets

Common FIRE Number Benchmarks

Here's a quick reference based on monthly spending:

• $3,000/month: FIRE number = $900,000 (Lean FIRE)
• $4,000/month: FIRE number = $1,200,000
• $5,000/month: FIRE number = $1,500,000
• $6,000/month: FIRE number = $1,800,000
• $8,000/month: FIRE number = $2,400,000 (Fat FIRE)
• $10,000/month: FIRE number = $3,000,000

Calculate Yours Now

Use the Quit Number calculator to find your FIRE number in 60 seconds. You'll get three numbers: your Quit Number (target), your Quit Score (how far along you are), and your Quit Date (when you'll get there). No account linking, no personal information — just answers.