QuietCalcsHow the projection works
Everything runs in real (inflation-adjusted) terms: you enter an investment return and an inflation rate, the calculator derives the real growth rate, and your withdrawal stays fixed in today's buying power — which means the actual withdrawals rise with inflation, the way real spending does. Each month the balance grows at the real rate and the withdrawal comes out; the projection ends when the balance does.
The tipping point is simple: if annual withdrawals are below real growth, the balance never falls and the answer is "indefinitely." Above it, the clock starts — and the closer you are to the line, the more sensitive the answer is to small changes, so test a few scenarios.
Some benchmarks
At a 6% return with 3% inflation (about 2.9% real):
| Balance | $2,000/mo | $3,000/mo | $4,000/mo |
|---|---|---|---|
| $300,000 | ~15.5 yrs | ~9.5 yrs | ~7 yrs |
| $500,000 | ~32 yrs | ~18 yrs | ~12.5 yrs |
| $750,000 | ~80 yrs | ~32 yrs | ~21 yrs |
Run your own numbers — the table is only a feel for the shape, and notice how close $750k at $2,000/month is to lasting forever: real growth on that balance is about $1,800/month.
The caveat that matters: sequence of returns
This projection uses a steady average return, but real markets deliver returns in a lumpy order — and when you're withdrawing, a crash in the first few years does far more damage than the same crash later, because you're selling more shares at low prices. That's why safe-withdrawal research (the source of the 4% rule) uses historical worst cases rather than averages, and why the honest reading of this tool is "roughly how long, if returns are ordinary" rather than a guarantee. For a margin of safety, test your plan with a return 1–2 points lower than you expect.
Frequently asked questions
How long will $500,000 last in retirement?
At $3,000/month in today's money with a 6% return and 3% inflation, about 18 years. Drop to $2,000/month and it stretches past 30 years; at about $1,100/month it lasts indefinitely, because withdrawals fall below real growth.
Do the withdrawals increase with inflation?
Yes — the withdrawal you enter is in today's buying power and effectively rises with inflation, which is how real retirement spending behaves. That's built into the real-rate math.
Does this include taxes?
No. If your withdrawals are taxed (traditional 401(k)/IRA and similar), enter the gross amount you'd need to withdraw to cover both spending and tax.
What about Social Security or a pension?
Subtract that income from your monthly withdrawal — the portfolio only needs to cover the gap.
Is my data stored?
Only in your own browser. Nothing is uploaded — the whole calculation runs locally.
Related calculators
Coast FIRE Calculator — the accumulation side of this exact math.
Barista FIRE Calculator — partial withdrawals with part-time income covering the rest.
Compound Interest Calculator — the same engine running forward instead of down.