Fat FIRE Calculator

Why Fat FIRE Needs Its Own Math

Fat FIRE is the high-budget end of the financial independence spectrum: retiring early without trimming your lifestyle, usually on something like $150,000 a year or more. At that level, two details that barely matter for a lean plan start to move the target by millions. First, the income a big portfolio throws off is taxed, so $200,000 of spending money means withdrawing noticeably more than $200,000. Second, early retirees may need their savings to last 50 or 60 years, and research on long horizons — notably the Early Retirement Now safe withdrawal rate series — points to rates around 3.25–3.5% rather than the classic 4% drawn from 30-year studies. This calculator builds both in.

Step by Step: Filling In the Form

Start with what you expect to spend each year once retired, in today's dollars and after tax — housing, travel, healthcare premiums, everything. Add an effective tax rate for your withdrawals: the share of each dollar withdrawn that goes to tax overall, not your top bracket. A mix of long-term capital gains, Roth money, and taxable-account withdrawals often lands well below wage tax rates, so 10–20% is a common planning range, but your own mix decides it. Choose a withdrawal rate (3.5% is the default here), then enter what you have invested now, what you add each month, and a real return, meaning the return after inflation. Because everything stays in today's dollars, the timeline answers "how many years until my money buys this lifestyle at today's prices."

The Formula Explained

Gross withdrawal = spending ÷ (1 − tax rate). Fat FIRE number = gross withdrawal ÷ withdrawal rate. The projection then grows your current balance month by month at the real return divided by 12 and adds your monthly contribution after each month, stopping when the balance reaches the target. The results table also shows what the target would be at 3%, 3.5%, and 4%, so you can see how sensitive the goal is to that one assumption.

A Real Example

Suppose you want $200,000 a year, expect a 15% effective tax rate, and plan on a 3.5% withdrawal rate. Gross withdrawal is $200,000 ÷ 0.85 = $235,294, and the Fat FIRE number is $235,294 ÷ 0.035 ≈ $6,722,689. Starting from $1,000,000 invested, adding $10,000 a month, and earning a 5% real return, the balance crosses that target after 238 months — about 19 years and 10 months. The same spending at a 4% rate with no tax adjustment would suggest just $5,000,000, a $1.7 million gap.

Edge Cases to Watch

A smooth average return hides sequence-of-returns risk: a deep market drop in the first few years of retirement can do lasting damage to a large portfolio that is being drawn down, and it's the main reason cautious rates exist. Flexible spending — cutting travel in a bad year — can matter as much as the headline rate. Before Medicare, private health insurance can be a large line item. Big one-off costs such as a second home or college tuition aren't level annual spending, so plan them separately. Treat the result as a planning estimate, not personalized tax or investment advice.