What is a FIRE calculator?
A FIRE calculator estimates how long it will take to become financially independent — the point where your invested savings are large enough that their returns can cover your living expenses, so working becomes optional. It centers on two numbers: your FIRE number (the portfolio you're aiming for) and the years to reach it given how much you save and earn on your investments. The math reveals a surprising truth — your income matters less than the percentage of it you keep. Because that percentage drives everything, check yours with the Savings Rate Calculator, then see how it compounds toward your number with the Compound Interest Calculator.
How to use this calculator
- Enter your age and current investments — the money already working for you in retirement and brokerage accounts.
- Enter your annual take-home income and expenses. The gap between them is what you invest each year.
- Set a real return and withdrawal rate (5% and 4% are common defaults) and press Calculate to see your FIRE number, years to FI, and the age you'll get there.
Example
A 30-year-old has $50,000 invested, earns $90,000 take-home, and spends $50,000 a year — a 44% savings rate. With a 4% withdrawal rate, their FIRE number is $50,000 × 25 = $1.25 million. Investing the $40,000 annual surplus at a 5% real return, they reach financial independence in roughly 18 years, at about age 48. Cut expenses to $40,000 and the timeline shrinks on both ends — they need less and save more.
Common mistakes & rules of thumb
FIRE (Financial Independence, Retire Early) comes down to one number and one habit. Keep these straight:
- Rule of thumb: your FIRE number is roughly 25× your annual expenses — the flip side of the 4% safe-withdrawal rule.
- Rule of thumb: your savings rate drives your timeline far more than your income. Someone saving 50% retires decades sooner than someone saving 10% at any salary.
- Common mistake: building the number off your income instead of your spending. FIRE is funded by what you actually need to live on, not what you earn.
- Common mistake: forgetting health insurance before Medicare age — a real, often large expense that early retirees must self-fund.
- Common mistake: assuming a withdrawal rate higher than 4% is safe. Sequence-of-returns risk means a bad first few years can sink an over-aggressive plan.
Frequently asked questions
What is FIRE?
FIRE stands for Financial Independence, Retire Early. You save and invest a large share of your income until your portfolio's returns can cover your living expenses indefinitely, freeing you from needing a paycheck.
What is my FIRE number?
It's the portfolio size that can sustainably fund your lifestyle — your annual expenses divided by your safe withdrawal rate. At a 4% withdrawal rate that's 25× your annual expenses.
What is the 4% rule?
From the Trinity Study: you can withdraw about 4% of your portfolio in year one of retirement, adjusting for inflation after, with a high chance the money lasts 30+ years. Conservative early retirees use 3–3.5%.
Why does my savings rate matter so much?
It's the biggest lever in early retirement. A higher savings rate grows your portfolio faster and lowers the FIRE number you need, because you live on less. Going from 20% to 50% can cut decades off the timeline.
Should I use a real or nominal return?
Use a real return — your expected return after inflation, around 5–7% for a stock-heavy portfolio historically. That keeps your FIRE number and result in today's dollars.