What Is Your FI Number? How to Calculate Financial Independence

Your FI number is the size your invested portfolio needs to reach so that it can fund your lifestyle without you ever working again. It's the most important number in personal finance — and it takes about 30 seconds to estimate.

The formula

Annual expenses × 25 = FI number. That's it. The 25× multiplier comes from the 4% rule, which we'll cover in another article. The short version: if your portfolio can sustainably withdraw 4% per year, then 25× your spending covers you indefinitely.

Three quick examples

• Spend $35,000/year → FI number ≈ $875,000
• Spend $50,000/year → FI number ≈ $1,250,000
• Spend $80,000/year → FI number ≈ $2,000,000

Why the number isn't as scary as it sounds

Two reasons. First, you're not saving the whole number — compounding does most of the heavy lifting. Investing $1,000/month at a 7% real return reaches $1M in about 28 years, even though you only contributed $336,000 yourself. Second, your FI number is tied to your spending, not your income. Trim $500/month from your lifestyle and your FI number drops by $150,000.

The two levers that move the date

Only two things determine when you reach FI: how much you invest each month and how much you spend each year. Income matters only insofar as it enables higher savings. A household earning $80K and saving $25K/year reaches FI faster than one earning $200K and saving $20K/year.

Get your real number

Open the Financial Freedom Calculator, enter your monthly expenses, and you'll see your FI number alongside the year you're projected to hit it given your current contributions.