What is Fat FIRE?
Fat FIRE is financial independence with room to spare. You stop working completely, and your investments and any pension pay for a life that is comfortable rather than careful: travel, eating out, help at home, generous gifts, and a buffer for the things you cannot plan.
FIRE stands for Financial Independence, Retire Early. People often split it by how much they plan to spend. Lean FIRE means retiring on a tight budget. Fat FIRE means retiring on a large one. Neither is better. They are different answers to the same question: what kind of life do you want your money to pay for?
Fat FIRE takes longer to reach, because the target is bigger. The reward is that you are less likely to need to cut back when markets fall or prices rise.
Your Fat FIRE number
Your Fat FIRE number is how much you need invested to stop work for good at your chosen level of spending. It depends on:
- how much you will spend each year,
- how much a pension will pay each year, if anything,
- and the withdrawal rate: the share of your investments you take out each year.
The sum takes your spending, subtracts your pension, and divides what is left by your withdrawal rate.
Fat FIRE number = (spending − pension) ÷ withdrawal rate
For example, a couple who want to spend $120,000 a year and expect $20,000 a year from pensions need their investments to pay $100,000 a year. At a 4% withdrawal rate that is $100,000 ÷ 0.04 = $2,500,000.
If they used a 3.5% withdrawal rate to be safer, the same $100,000 would need about $2,857,000. At 3%, it would need about $3,333,000. Small changes in the withdrawal rate move a Fat FIRE number by hundreds of thousands, so it is worth deciding what you are comfortable with.
When you get there
The calculator shows the age you reach your Fat FIRE number. It starts from what you have invested today and steps forward one year at a time. Each year your investments grow at the real growth rate, and a year of your monthly saving is added. The first age at which your investments are at least your number is your Fat FIRE age.
The real growth rate is growth after inflation:
real rate = (1 + growth) ÷ (1 + inflation) − 1
With 7% growth and 3% inflation that is 1.07 ÷ 1.03 − 1 = 3.88% a year. This is the same rate and the same yearly steps the Coast FIRE calculator uses. Every amount is in today’s money, so $2,500,000 means $2,500,000 of today’s spending power.
Take a couple aged 30 with $150,000 invested who add $1,200 a month. At that pace they reach $2,500,000 at 75, which is later than most people would call early. Saving $3,000 a month brings it to 61. Saving $5,000 a month brings it to 53. Spending $100,000 instead of $120,000, with the same $20,000 pension, lowers the number to $2,000,000, and at $3,000 a month they reach it at 57.
Fat FIRE is mostly a high-income goal, or a long one. The calculator makes that honest trade-off visible: you can see exactly what each extra amount of saving or spending does to your age.
How to use this calculator
- Choose your country. This sets your currency, how numbers are written, a default inflation rate and the name of your state pension. Taxes are not calculated for any country yet.
- Choose Just me or Couple. For a couple, enter money as household totals.
- Enter what you have invested and what you add each month. Include retirement accounts, index funds and other long-term investments. Leave out your home and your emergency fund.
- Enter what you want to spend each year in retirement, in today’s money. Be generous: that is the point of Fat FIRE.
- Enter your pension income per year. If you are not sure, enter 0. That is the cautious choice.
The answer updates as you type. Every step of the maths is shown under “How we calculated this”, filled in with your own numbers. To change growth, inflation or the withdrawal rate, press Change.
If you have already saved a plan on the Coast FIRE calculator, this page fills in your country, ages, savings, pension and assumptions from it. Your spending stays at the higher Fat FIRE level until you change it.
Things to think about
Spending in retirement is not flat. Many people spend more in their first active years and less later, then more again on care. Use an average you are comfortable with.
Pensions often start later than an early retirement. If yours starts years after you stop work, your investments must cover the gap on their own. This calculator does not yet handle those gap years. Enter a lower pension figure to stay on the safe side.
Taxes and fees are not included. Withdrawals from many accounts are taxed, and large portfolios can carry noticeable fees. Treat the result as a before-tax estimate and aim a little higher.
A longer retirement needs a safer rate. The 4% rate comes from US research on 30-year retirements. If you plan to stop at 50 and live to 95, many people choose 3% or 3.5%.
Fat FIRE, Coast FIRE and Barista FIRE
These ideas fit together.
- Coast FIRE: when can I stop saving for retirement and let growth do the rest? Try the Coast FIRE calculator.
- Barista FIRE: when can I leave full-time work and live on part-time pay plus my investments? Try the Barista FIRE calculator.
- Fat FIRE: how much do I need to stop work completely and live generously?
They are not either-or. Reaching Coast FIRE early takes pressure off. Barista FIRE can be a comfortable stop on the way. Fat FIRE is the finish line for people who want full freedom with no compromise on lifestyle.