The Trinity Study's 4% answer says "30+ years" — but that's for a $1M portfolio spending exactly $40K/year. What about $1M spending $60K? Or $3M spending $80K? Below is the math and a complete table for portfolios from $1M to $5M at typical spending levels.
The math, in one paragraph
For a constant inflation-adjusted withdrawal W from a portfolio P earning real return r, the portfolio depletes in roughly n = ln(W / (W − P·r)) / ln(1 + r) years. If W ≤ P·r, the math says "indefinite" — your portfolio earns more than you withdraw and your principal is never touched. The table below assumes a 5% real return (more conservative than the historical 7% real for stocks-only).
Table: how long each portfolio lasts at each spending level
Assumes 5% real (inflation-adjusted) return, constant inflation-adjusted withdrawals, no taxes modeled. "Indefinite" means withdrawal is at or below the portfolio's real growth.
| Annual spending | $1M | $2M | $3M | $5M |
|---|---|---|---|---|
| $40,000/yr | indefinite | indefinite | indefinite | indefinite |
| $60,000/yr | 37 yrs | indefinite | indefinite | indefinite |
| $80,000/yr | 20 yrs | indefinite | indefinite | indefinite |
| $100,000/yr | 14 yrs | indefinite | indefinite | indefinite |
| $150,000/yr | 8 yrs | 23 yrs | indefinite | indefinite |
The headline numbers
- $1M lasts: indefinitely at $40K/year, ~25 years at $60K, ~14 years at $80K, ~10 years at $100K.
- $2M lasts: indefinitely at $80K/year, ~25 years at $120K, ~14 years at $160K.
- $5M lasts: indefinitely at any spending level up to $250K/year (5% of $5M). Above that, depletes proportionally.
The real-world caveats
The table above is the deterministic compound-interest answer. Three things can shorten it substantially:
- Sequence-of-returns risk. Bad market returns in the first decade of retirement permanently shrink the portfolio. Two retirees with the same lifetime average return can have wildly different durations — see our sequence-of-returns post.
- Higher real spending. "Inflation-adjusted" assumes your spending tracks CPI. Healthcare in early retirement often outpaces CPI by 2-3 percentage points. Lifestyle inflation (the "creep") can also push real spending up unintentionally.
- Lower real returns going forward. Recent valuation-aware research (Pfau, Morningstar) argues for 4-5% real returns instead of the historical 7% — putting the "safe forever" level closer to 4% withdrawal rather than 5%.
Want a more conservative estimate?
For a 50+ year early retirement, divide the table's "indefinite" threshold by 1.25 — i.e., treat 4% as the safe rate instead of 5%. So $1M is "indefinite" at $40K/year; $2M at $80K/year; $5M at $200K/year. The conservative path uses our 4% rule calculator with the 3.5% slider for additional cushion.
The honest answer
How long $1M lasts depends mostly on how much you spend. The math is unforgiving above the safe-withdrawal threshold and forgiving below it. If you want $1M to last forever, find a way to live on $40-50K/year. If you want to spend $80K/year, plan for a $2M portfolio or expect to deplete a $1M portfolio in about 14 years.