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Reference material for the numbers Promi computes, written to be read by someone who has not done this before.

FIRE & Financial Independence

The arithmetic behind financial independence, and the variants people build around it.

FIRE (Financial Independence, Retire Early)
Accumulating enough that investment income covers expenses, well before conventional retirement age.
FI Number
The portfolio value at which investment income covers annual expenses indefinitely.
The 4% Rule (Safe Withdrawal Rate)
A withdrawal rate calibrated so a portfolio survived every historical 30-year window tested.
Lean FIRE
Financial independence built on a deliberately low spending level.
Fat FIRE
Financial independence at a spending level that requires no reduction in lifestyle.
Barista FIRE
A portfolio covering most expenses, with part-time work closing the gap and supplying benefits.
Coast FIRE
Having enough invested that growth alone reaches the target by retirement age, with no further contributions.
Sequence of Returns Risk
The risk that poor returns arrive early in retirement, when withdrawals compound the damage.
Monte Carlo Simulation
Testing a plan against thousands of randomized return sequences instead of one average.

Worked examples for every term

This content is educational and informational only. It is not financial, investment, or tax advice. Consult a qualified professional before making financial decisions.

Every one of these explains a number in the app

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