A Simple Bitcoin FIRE Calculator
Keeping It Simple
Prior Bitcoin FIRE Discussions:
Bitcoin Retirement or Bitcoin FIRE
An Oversimplified Approach to Bitcoin FIRE
FIRE E-guide
A Simple Bitcoin FIRE Calculator
I built a simple calculator to explore Bitcoin-based FIRE.
Not to predict prices.
Not to optimize trades.
Not to tell you when to retire.
It simply explores:
What does financial independence look like if you treat Bitcoin as a long-term reserve instead of a monthly income source?
What the Calculator Is
This is a cash-runway + Bitcoin reserve model, not a traditional withdrawal-rate calculator.
It models three things over time:
Cash: your short-term spending buffer
Bitcoin: a long-term reserve you try not to touch
Time: how long you can wait through volatility without being forced into bad decisions
Instead of asking “Will my portfolio last forever?” it asks:
“How much optionality do I have, and how fragile is my plan?”
How to Use It (at a High Level)
Enter your annual spending
Choose a Bitcoin FIRE model (Lean / Coast / Fat)
Each model has simple assumptions:
Cash multiple (e.g. 3× annual spending)
Bitcoin multiple (e.g. 5×, 10×, 25×)
Pick an exit date
The point where you stop relying on full-time fiat work
The calculator then:
Walks forward month by month using historical BTC prices
Spends from cash
Tracks Bitcoin without selling unless rules allow it
Shows when cash runs out, refills, or forces adaptation
Note: Currently the calculator rebalances cash whenever a new All Time High is reached.
You can edit all assumptions. Nothing is hard-coded.
What It Shows (and What It Doesn’t)
It shows:
How long a given cash runway actually lasts
What different exit timing looks like historically
How often you’d need to adapt (work, cut spending, wait)
The difference between fragile and resilient plans
It does not show:
Guaranteed outcomes
Optimal selling strategies
A “safe” forever withdrawal rate
Why This Is Valuable
Most FIRE tools assume:
smooth returns
regular withdrawals
low volatility
Bitcoin breaks those assumptions.
This calculator:
respects Bitcoin’s volatility instead of smoothing it away
makes timing risk visible
turns abstract ideas (“I’ll just wait it out”) into something concrete
helps people see the tradeoff between independence vs certainty
Even if you never “retire,” visualizing these paths is useful.
You can see:
when plans get tight
when flexibility matters
where overconfidence creeps in
How I Think About It
Bitcoin doesn’t eliminate work.
It changes the terms of work.
This tool isn’t about escaping responsibility.
It’s about understanding when you have leverage, and when you don’t.
Use it to stress-test assumptions.
Use it to compare paths.
Use it to be more honest with yourself.
For me, simply scrolling through this spreadsheet helps tether the theoretical to the practical.
Version 2
What would you like to see in a Version 2 of this spreadsheet?
If I extend this, the next things I’d explore are:
more flexible cash top-up rules (partial refills, different triggers)
adjustable sell thresholds beyond a simple ATH
inflation-adjusted spending
But even in its current form, the goal is simple:
make tradeoffs visible, without pretending certainty exists.
Did I make a mistake in V1? Please leave a comment with any errors or corrections.