How Long Will My Money Last?

How it works

This is the question the famous "4% rule" was invented to answer. In 1994, financial planner William Bengen tested withdrawal rates against every 30-year stretch of US market history he had and found that starting at 4% of the portfolio (adjusted for inflation each year) had never exhausted a stock-and-bond mix. The 1998 Trinity study — three professors at Trinity University — ran a similar sweep across portfolio blends and reached broadly the same place, and "4%" became shorthand for a safe-ish starting withdrawal.

This calculator is simpler than either study, on purpose: a fixed monthly withdrawal, a constant return, one balance evolving month by month. The defaults hold a small discovery. Withdrawing $4,350 a month from $1,250,000 is a 4.2%-a-year pace — but at a 5% return, the pot earns about $5,208 a month, more than you're taking out. The balance rises, and the line never comes down. Drag the return slider to 3% and the same withdrawal starts eating principal; at 2%, the pot is gone in about 33 years. The gap between "grows forever" and "gone" is startlingly thin.

Here's why a steady-return line flatters you: real markets pay their average unevenly, and the order matters. Two retirements with identical average returns can end decades apart if one meets a crash in year two — every withdrawal during the downturn sells more of the portfolio at low prices, and the damage compounds. That's sequence-of-returns risk, this page can't model it, and it's exactly what ClariFi's Retirement Lab is for: it stress-tests this same question against 5,000 simulated market histories built on data back to 1928, and reports a success probability — not a single line that was never going to happen.

The formula

each month: balance = balance × (1 + r/12) − W
stop when balance ≤ 0, or after 40 years
never depletes when W ≤ balance × r/12   ← withdrawing under the interest
Example: $1,250,000 at 5%/yr earns ≈$5,208/mo
         a $4,350/mo withdrawal never touches principal by this math

Honest assumptions

• The return arrives smoothly, every month, forever — no crashes, no recoveries, no sequence risk. Real retirements get none of that courtesy.
• The withdrawal never changes. There's no inflation adjustment — if you want one, treat the return slider as a real (after-inflation) return and the withdrawal as today's dollars.
• No taxes, no fund fees, no advisor fees. All of them make the money last less long than this page says.
• The chart stops at 40 years; "40+" means the money outlived the window, not that it's infinite.
• This page does arithmetic. It doesn't know your life — it's a starting point, not a plan, and not advice.

Questions people ask

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ClariFi makes tools, not advice. Nothing on this page is a recommendation to buy, sell, or sign anything.