FIRE glossary
FIRE Number (Target Pot)
The portfolio size that would let you sustain your planned annual spending, from retirement to the end of your life expectancy, without further paid work.
How it's built
Your FIRE number depends entirely on the withdrawal basis you've chosen. On the standard or custom safe-withdrawal-rate basis it's annual spend ÷ SWR — 25× spend at a 4% rate, roughly 30.8× at a more conservative 3.25%. On a drawdown-to-zero basis it's the present value of an annuity over your specific horizon (life expectancy minus retirement age) at your assumed real return, which for most horizons comes out smaller than the SWR figure because it deliberately targets a pot that runs out on schedule rather than one that, mathematically, never does. The two bases can disagree by a wide margin for the same spend and horizon — see the drawdown-to-zero term for why.
It moves with more than your spending
A legacy target — money you want left over rather than spent — raises the floor beneath the required pot. Retiring before your pensions or state benefits start adds a bridge-period lump on top, sized to fund the gap years on their own. None of these are separate figures you have to reconcile by hand: Ember's engine folds every applicable overlay into the one required-pot number and shows the trace behind it, so the headline figure is never a black box.
One number, several honest caveats
A FIRE number computed today is only as good as the assumptions feeding it — the withdrawal rate, the real return, the inflation figure. Ember's engine flags an unusually aggressive or conservative SWR choice and an inflation assumption that looks out of range, and every figure carries the full maths trace that produced it rather than presenting a bare, unexplained number.
Why it changes over time
Your FIRE number isn't fixed the day you first calculate it — it moves as your spending target, assumptions, tax residency, and any planned events (a house purchase, an inheritance, a pension you add) change. Re-checking it periodically, rather than treating one calculation as permanent, is how the number stays a useful target instead of going stale.
Worked example
A $50,000/yr spending target, at a 4% SWR
FIRE number
US$1,250,000
requiredPot = annual spend ÷ SWR
Fixed illustrative inputs, not your data — for the exact maths behind your own numbers, use the free calculator or build a plan. Educational modelling, not financial advice.
Across borders
Moving countries changes both the tax gross-up behind your required pot and — if you also plan to relocate physically — the cost of living behind your annual spend, so the same lifestyle can carry a materially different FIRE number in a different country. See the geoarbitrage term and /countries.
Common questions
Is my FIRE number the same regardless of where I live?
No — it's grossed up for tax on the taxable share of your withdrawal, so the required pot changes with your tax residency even at the same spending target and withdrawal rate.
Does the FIRE number include a safety margin?
Not automatically — it's the bare-minimum pot at your chosen withdrawal basis. Widen the margin deliberately: lower your custom SWR, add a legacy target, or check the plan's Monte Carlo success probability rather than assuming a buffer is already built in.
How is this different from Coast FIRE or Barista FIRE?
Your FIRE number is the target itself. Coast FIRE and Barista FIRE are two different routes toward reaching (or partially reaching) that same target sooner — see those terms.
Related terms
See fire number (target pot) in your numbers
The free calculator gives a rough estimate; the full planner models your actual accounts, pensions, residency moves and taxes — with the maths behind every figure shown.