Key takeaways
- The rate converts spending into a target: 4% implies 25×, and 3% implies roughly 33×.
- “Safe” meant surviving historical 30-year sequences — a reference point, not a guarantee.
- Longer horizons argue for lower rates and flexibility argues for higher ones; the spread across rates is the honest answer.
The number that sizes everything
A withdrawal rate is the share of a portfolio you draw in the first year of retirement, typically raised with inflation thereafter. Invert it and you get the multiple of spending you need: 4% implies 25× annual spending, 3.5% implies about 28.6×, 5% implies 20×. Every FIRE number on this site is that division and nothing more.
Example · one budget, three mountains
Spending of $48,000/yr needs $1,371,000 at 3.5%, $1,200,000 at 4%, and $960,000 at 5%. Same life — the rate alone moved the target by $411,000.
Where 4% came from
The figure traces to research on historical US market sequences — most famously the “Trinity study” framing — asking what starting rate survived every rolling 30-year period. “Safe” meant “did not run out in the historical record,” which is an important and humble claim: the past constrains the estimate, it does not underwrite the future.
What moves your number
Longer horizons argue for lower rates — a 50-year early retirement is a harder problem than the 30-year case the research studied. Flexibility argues for higher ones: a retiree who can trim spending in bad years takes real pressure off the math. Fees, taxes, and allocation all tug at the edges. There is no universally right rate; there is a rate whose assumptions you can state out loud.
Using it without worshipping it
Treat the rate as a planning dial, not a law. Run your plan at 3.5%, 4%, and 4.5% and look at the spread in required portfolio — that range is the honest answer. The withdrawal calculator here models the drawdown month by month so you can watch the mechanics rather than trust a slogan.
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