Savings Drawdown Calculator (How Long Will It Last?)
Enter your starting balance, the fixed amount you plan to withdraw each month, and the return you expect the remaining balance to earn. This calculator finds how many months and years the money lasts before it runs out — or tells you when your withdrawal is small enough that interest alone covers it and the balance never depletes. It uses a constant return, so treat the result as a planning estimate, not a guarantee.
Balance & withdrawal
Returns are applied to the balance each month; the withdrawal is then subtracted. Use a real (inflation-adjusted) return if your withdrawal is in today's dollars.
Your savings last
23.76 yrs
285 months until the balance reaches $0
First-month interest
$2,083.33
Monthly withdrawal
$3,000.00
Drawdown detail
Balance over time
Compare scenarios
Run the same calculation with two or three input sets side by side. Differences are highlighted; every number comes from the same tested formula as the calculator above.
| Input | Scenario A | Scenario B |
|---|---|---|
| Principal | ||
| Monthly Withdrawal | ||
| Annual Return Pct |
How it works
Each month the remaining balance earns a return, then your withdrawal is subtracted. The monthly rate is your annual return divided by twelve. When the interest earned in the first month (balance × monthly rate) is already larger than your withdrawal, the balance grows instead of shrinking and the calculator reports that it never depletes. Otherwise the balance falls a little further each month until it reaches zero.
For a depleting balance, the number of months is solved in closed form with the annuity-exhaustion formula: months = −ln(1 − r·PV/PMT) ÷ ln(1 + r), where PV is your balance, PMT is the monthly withdrawal, and r is the monthly rate. When the expected return is zero, that simplifies to balance ÷ withdrawal — you simply spend down the pot with no growth. Years are just months divided by twelve.
The chart traces the balance declining toward zero over time so you can see the shape of the drawdown: growth slows the decline early on, then the balance falls faster as the interest it throws off shrinks. Because the model applies one steady return every month, it deliberately ignores market volatility — real returns arrive in an uneven sequence, and the order they arrive in matters as much as the average.
Frequently asked questions
How does this relate to the 4% rule?+
The 4% rule is a different lens on the same problem. It asks what withdrawal rate a portfolio can sustain for a fixed retirement length (classically 30 years), whereas this tool fixes your withdrawal and solves for how long the money lasts. If your annual withdrawal is roughly 4% of your balance, you will generally see the money stretch for decades here — and a small enough withdrawal relative to your return will show as never depleting. Neither approach is a promise of safety; both are simplified planning models, and this is not financial advice.
Why doesn't a constant return reflect real markets?+
Real returns are volatile: a portfolio might gain 20% one year and lose 15% the next, even if the long-run average looks smooth. This calculator applies the same return every single month, which hides that bumpiness. The danger it cannot show is sequence-of-returns risk — a run of poor returns early in your drawdown forces you to sell more shares while prices are low, permanently shrinking the balance even when the long-term average is fine. Two retirees with identical average returns can run out years apart purely because of the order in which good and bad years arrived.
What return rate should I enter?+
It depends on whether you are thinking in today's dollars or future dollars. If your withdrawal is in today's purchasing power, use a real (inflation-adjusted) return — historically something like 3–5% for a diversified portfolio — so the answer reflects how long the money lasts in real terms. If you use a nominal return, your withdrawal should also grow with inflation, which this tool does not model. To stay conservative, try a lower return and a slightly higher withdrawal than you expect, and see whether the timeline still holds. This is a planning estimate, not advice.