How to Calculate Your FIRE Number

What is a FIRE number?

Your FIRE number is the total portfolio value you need so that investment returns alone can cover your living expenses indefinitely — without ever touching a job again.

The concept is simple: once your portfolio is large enough, it generates more income each year than you spend. You've reached Financial Independence. The Retire Early part is optional — many people hit FI and keep working, just on their own terms.

The 4% rule — where the number comes from

The FIRE number is built on the 4% rule, which comes from the Trinity Study (1998) — a landmark analysis of historical US stock and bond market data. The finding: a portfolio invested in a 60/40 stocks-bonds split could sustain a 4% annual withdrawal for 30 years with a very high success rate across historical periods, including the Great Depression.

In practice this means: if your annual expenses are $50,000, you need a portfolio of $1,250,000. If expenses are $80,000, you need $2,000,000.

The four FIRE variants

The standard 4% rule is just the starting point. Different lifestyles and risk tolerances produce different multipliers:

Lean FIRE

Lean FIRE uses a 5% withdrawal rate (20× expenses). You retire earlier, but your lifestyle will be genuinely frugal. Popular with people who want maximum speed and are comfortable with geographic arbitrage — living in lower-cost countries where $25,000/year goes a very long way.

Regular FIRE

The classic. 25× annual expenses at a 4% withdrawal rate. This is the benchmark most FIRE communities use. If your expenses are $50,000/year, your target is $1.25M. Historically this has survived all major market downturns over 30+ year periods.

Fat FIRE

Fat FIRE uses a more conservative 3–3.5% withdrawal rate (28–33× expenses), giving you a larger safety buffer and more spending power in retirement. The cost is a longer accumulation phase. Popular with higher earners who don't want to compromise their lifestyle.

Barista FIRE

The pragmatist's choice. You semi-retire — quit the stressful career, work part-time to cover basic expenses, and let a smaller portfolio cover the rest. The name comes from the idea of working at a café for the social connection, moderate income and (in the US) employer healthcare benefits. Your required portfolio drops dramatically because you're only asking it to cover a portion of expenses.

Coast FIRE — the version you might have already hit

Coast FIRE is different from the others. Instead of asking "how much do I need at retirement?" it asks: "How much do I need invested right now, so that compound growth alone reaches my FIRE number by retirement age — without saving another cent?"

If you're 35 and want to retire at 65, your money has 30 years to compound at ~7%/year. A portfolio of $230,000 today grows to roughly $1.75M by 65 without any additional contributions. If $1.75M is your FIRE number, you've already hit Coast FIRE.

This is enormously liberating. Many people in their mid-30s have already crossed this threshold without realising it. Once you hit Coast FIRE, you can stop saving aggressively and work entirely on your own terms — lower-stress job, part-time, passion project.

Geographic arbitrage — the FIRE accelerator

One of the most underused levers in FIRE planning is location. Your FIRE number is calculated from your expected expenses. If you retire in Portugal instead of California, your expenses might drop 50%. That means your required portfolio drops 50% too.

A Lean FIRE number of $600,000 in a high-cost city becomes a very comfortable retirement in Lisbon, Chiang Mai, Medellín or Tbilisi. The FIRE community calls this geographic arbitrage — earning in a high-income country and spending in a lower-cost one.

The savings rate is everything

Your savings rate — the percentage of income you save and invest — is the single most powerful variable in your FIRE timeline. Not your income. Not your investment returns. How much you save.

Here's why: a higher savings rate does two things simultaneously. It increases the amount you're investing each month, and it reduces your annual expenses (since you're spending less). Both of those compress your FIRE timeline dramatically.

• Saving 10% of income → roughly 40 years to FI
• Saving 25% of income → roughly 32 years to FI
• Saving 50% of income → roughly 17 years to FI
• Saving 75% of income → roughly 7 years to FI

The numbers above assume you start from zero and earn 7% real returns. The exact numbers vary, but the principle is stark: each 5% increase in savings rate shaves years off your timeline, not months.

What FIRE type are you?

Not sure which variant fits your life? The answer depends on your relationship with work, your lifestyle expectations, your risk tolerance and your flexibility around location. A 7-question quiz can help narrow it down to a personalised FI number and recommended path.

Common FIRE number mistakes

• Not accounting for inflation. Your expenses will rise. Build in a buffer or use a slightly lower withdrawal rate (3.5% instead of 4%).
• Assuming fixed expenses. Healthcare, family changes and housing costs all shift over a 30-year retirement. Model your expenses with some flexibility.
• Ignoring sequence of returns risk. A major market crash in the first 2–3 years of retirement is far more damaging than one 20 years in. A cash buffer or a lower initial withdrawal rate protects against this.
• Underestimating lifestyle inflation. As income rises, expenses tend to rise with it — often invisibly. Every $1,000/year in new lifestyle spending adds $25,000 to your FIRE number.
• Not using tax-advantaged accounts. Super, 401k, ISA, RRSP — the exact wrapper depends on your country, but tax-advantaged compounding dramatically accelerates accumulation.

FAQ