Fat FIRE Calculator
Find the portfolio you need to retire on a comfortable, no-compromise income — and see your Lean, Regular and Fat FIRE numbers side by side at any safe withdrawal rate. Enter your spending and savings; the target, the age you'd reach it, and the exact formula update instantly. No sign-up.
Return & inflation assumptions
Returns are handled in real (after-inflation) terms, so every dollar shown is in today's money.
Quick answer
Spending $100,000 a year at a 4% withdrawal rate means a $2,500,000 Fat FIRE number. From $200,000 invested at age 35, adding $3,000 a month at a 3.88% real return, you would reach it at about age 64 — 29 years away. Change the inputs above and this answer updates with your own numbers.
Lean vs Regular vs Fat FIRE — at your withdrawal rate
Same formula, three lifestyles. Your own spending decides which tier you're aiming at (highlighted).
| Tier | Annual spending | Portfolio needed |
|---|
Getting to your number
Green = your projected portfolio (today's dollars). Indigo = your FIRE target. Where they meet is the age you reach it.
How your monthly contribution moves the date
Everything else held equal — see how saving more or less shifts the age you hit your number.
| Monthly contribution | Reached at | From now |
|---|
Lean, Regular and Fat — the same formula, three lifestyles
Every FIRE variant uses one calculation: annual spending divided by your safe withdrawal rate. The tiers are not different maths, only different spending assumptions.
| Tier | Typical annual spending | Portfolio needed at 4% |
|---|---|---|
| Lean FIRE | $40,000 | $1,000,000 |
| Regular FIRE | $70,000 | $1,750,000 |
| Fat FIRE | $120,000 | $3,000,000 |
The thresholds are conventions rather than definitions, and they vary between sources. What does not vary is the multiplier: at a 4% withdrawal rate every tier is simply 25 times annual spending.
The uncomfortable arithmetic of a bigger lifestyle
Because the number is a multiple of spending, lifestyle inflation is expensive in a very specific way: every extra $10,000 of annual spending adds $250,000 to the target. Same starting position — age 35, $200,000 invested, $3,000 a month — varying only the lifestyle:
| Annual spending | Number needed | Age reached | Years of work |
|---|---|---|---|
| $60,000 | $1,500,000 | 55 | 20 |
| $100,000 | $2,500,000 | 64 | 29 |
| $150,000 | $3,750,000 | 72 | 37 |
| $200,000 | $5,000,000 | 78 | 43 |
Moving from a $60,000 lifestyle to a $100,000 one costs nine additional years of working. Moving to $200,000 costs twenty-three. The spending figure is not a detail in this calculation — it is the calculation.
The withdrawal rate is an assumption, and it moves the answer years
The 4% figure comes from research into historical portfolio survival and is a planning convention, not a law. Fat FIRE plans often use a lower rate, on the reasoning that a longer retirement deserves more caution. That caution has a price:
| Withdrawal rate | Number needed for $100,000/yr | Age reached |
|---|---|---|
| 3.0% | $3,333,333 | 70 |
| 3.5% | $2,857,143 | 67 |
| 4.0% | $2,500,000 | 64 |
| 5.0% | $2,000,000 | 60 |
Dropping from 4% to 3% — a common instinct for a long retirement — adds $833,333 to the target and six years to the timeline. Moving to 5% takes four years off and raises the risk of running short. There is no correct row; there is a trade between the risk of running out of money and the risk of spending years earning money you did not need.
What you save each month
Same $2,500,000 target from $200,000 at 35:
| Monthly contribution | Age reached | Years |
|---|---|---|
| $2,000 | 70 | 35 |
| $2,500 | 67 | 32 |
| $3,000 | 64 | 29 |
| $4,000 | 60 | 25 |
| $5,000 | 57 | 22 |
An extra $3,000 a month — from $2,000 to $5,000 — brings the date forward by thirteen years. Notice that this is the same lever as the spending table, viewed from the other side: money not spent is money saved, so it moves both columns at once. That is why the gap between income and spending, rather than income alone, decides how early anyone reaches any of these tiers.
The things that quietly break Fat FIRE plans
- Lifestyle creep during accumulation. Spending that rises with income raises the target while reducing the amount available to reach it.
- Healthcare before Medicare. A large and volatile expense that must be in the spending figure, not assumed away.
- Sequence-of-returns risk. A poor first decade of withdrawals damages a portfolio far more than the same decade later, and a longer retirement means more exposure to it.
- Real returns, not nominal. This calculator uses a real return — (1 + nominal) ÷ (1 + inflation) − 1, which is 3.88% for the default 7% and 3% — so the target stays in today's money. Using a nominal return against a today's-money target is the most common error in FIRE arithmetic.
The method
Then the calculator projects your current balance and monthly contributions forward at the real return until the balance first reaches that number, which gives the age. Everything is expressed in today's dollars, so the target and the projection are directly comparable.
See the method with your own numbers
These update live from the calculator inputs above.
Example: a $100,000 lifestyle from age 35
- Target: $2,500,000 — $100,000 divided by 4%.
- Reached at about age 64, 29 years from a $200,000 start at $3,000 a month.
- Trim spending to $60,000 and the same plan finishes at 55.
- Raise saving to $5,000 a month and the $100,000 lifestyle arrives at 57.
Those last two lines are the whole strategy. You can reach Fat FIRE by earning and saving more, or by needing less — and because spending sits in both the target and the savings rate, reducing it moves the date roughly twice as hard.
Frequently asked questions
What is Fat FIRE?
Financial independence at a comfortable, unconstrained level of spending rather than a frugal one. There is no official threshold, but it commonly describes plans built around roughly $100,000 or more of annual spending, which at a 4% withdrawal rate means a portfolio of $2,500,000 or more.
How much do I need for Fat FIRE?
Twenty-five times your annual spending at a 4% withdrawal rate. $100,000 a year needs $2,500,000; $150,000 needs $3,750,000; $200,000 needs $5,000,000. Lower the withdrawal rate and the multiple rises — at 3% it becomes 33 times, so $100,000 a year would need $3,333,333.
What is the difference between Lean, Regular and Fat FIRE?
Only the spending assumption. All three use the same formula. Conventionally Lean FIRE describes roughly $40,000 a year ($1,000,000 at 4%), Regular around $70,000 ($1,750,000) and Fat around $120,000 ($3,000,000). The boundaries vary by source and by where you live.
Is a 4% withdrawal rate safe for Fat FIRE?
It is a planning convention drawn from historical research, not a guarantee, and a longer retirement gives it more chances to fail. Many Fat FIRE plans use 3% to 3.5% for that reason. The cost is explicit: moving from 4% to 3% adds $833,333 to a $100,000 lifestyle target and about six years to the timeline.
How much does spending less actually help?
Twice over. Every $10,000 of annual spending removed cuts the target by $250,000, and the money not spent can be saved instead. In the default plan, a $60,000 lifestyle arrives at 55 while a $100,000 lifestyle arrives at 64 — nine years, from spending alone.
Should I use a real or nominal return?
Real, and this calculator does it for you: 7% nominal against 3% inflation is a 3.88% real return, not 4%. Because your spending target is in today's money, the projection has to be as well. Mixing a nominal return with a today's-money target is the most common mistake in FIRE calculations and makes the date look years closer than it is.
Method & sources
- Calculation: FIRE number = annual spending ÷ safe withdrawal rate; the age you reach it is a month-by-month projection of current investments plus contributions at a real (after-inflation) return. Verified in an independent test suite.
- Concepts (Lean/Regular/Fat FIRE, safe withdrawal rate, 25× rule) follow standard FIRE-community definitions; figures are illustrative, not forecasts.
- Reviewed: · Assumptions reviewed quarterly.
Educational estimate, not financial advice. Investment returns are not guaranteed.
Run your own numbers
Enter your target spending, withdrawal rate and what you save each month, and see your number and the age you would reach it.
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