What Is My FIRE Number? (And How Do I Calculate It?)

FIRE stands for Financial Independence, Retire Early.

The goal is simple: save and invest enough money so your investments can cover your living expenses indefinitely.

Instead of working for money, your money works for you.

Once your investments generate enough income to cover your expenses, you have reached financial independence. Retirement becomes optional.

The key question becomes: how much money do I need invested to make that happen? That number is your FIRE number.

The most common way to calculate your FIRE number is using the 25x rule.

Formula: Your FIRE Number = Annual Expenses x 25.

Why 25? It comes from the 4% rule, based on research from Trinity University, often called the Trinity Study.

The research found that historically you could withdraw 4% per year, adjust for inflation, and your money would likely last 30+ years.

If you withdraw 4%, that means you need 1 ÷ 0.04 = 25. So you need 25 times your annual expenses invested.

Step 1: Calculate your annual expenses. This is the most important step.

Not your income. Not what you think you spend. Your actual yearly expenses.

If you spend $60,000 per year, your FIRE number would be: $60,000 x 25 = $1,500,000.

Your FIRE number is $1.5 million.

Here is how it looks across different lifestyles:

As you research "what is my FIRE number," you will see different variations.

Lean FIRE uses lower annual expenses and a smaller FIRE number.

Fat FIRE assumes a higher spending lifestyle and a larger FIRE number.

Coast FIRE means you have invested enough that it will grow to your FIRE number without further contributions.

Each version changes the math slightly but the foundation is still the 25x rule.

1. Using income instead of expenses. Your FIRE number is based on what you spend, not what you earn.

2. Forgetting taxes. Investment withdrawals may be taxable based on account types.

3. Ignoring healthcare. Healthcare costs before Medicare can significantly impact early retirees.

4. Assuming 4% always works. It is historical guidance, not a guarantee.

If you want a safer estimate, use Annual Expenses ÷ 0.035 = FIRE Number.

Example: $60,000 ÷ 0.035 = $1,714,285.

5. Not adjusting for lifestyle changes. Travel, location, and mortgage changes can shift expenses.

Your timeline depends on savings rate, investment returns, current portfolio value, and annual contributions.

This is where most people guess instead of calculate. The math matters.

You can calculate it manually, or you can run the numbers instantly and see your FIRE number, years to financial independence, required savings rate, and projected portfolio growth.