Retirement Withdrawal Calculator - How Long Will Your Money Last?
How long a retirement portfolio will last under regular withdrawals is the most practically important calculation in all of personal finance. The formula: n = -ln(1 - (Balance x r / Annual Withdrawal)) / ln(1 + r).
The Formula Explained
Worked example: Sandra has $480,000, withdraws $42,000/year, expects 5 percent return. n = -ln(1 - (480,000 x 0.05 / 42,000)) / ln(1.05) = 17.4 years - until age 82 if currently 65. Reducing withdrawals to $32,000: extends to 34.5 years.
| Portfolio Balance | Annual Withdrawal | Return | Years Portfolio Lasts |
|---|---|---|---|
| $500,000 | $25,000 (5%) | 6% | Never depletes |
| $500,000 | $40,000 (8%) | 6% | ~24 years |
| $500,000 | $50,000 (10%) | 6% | ~15 years |
| $500,000 | $60,000 (12%) | 6% | ~11 years |
How to Use This Calculator on CalcAdvisor.com
Run your withdrawal longevity calculation at https://www.calcadvisor.com/calculators/retirement-withdrawal-calculator.
3 Real-World Examples
Example 1: Charles, 68, Testing Sustainability
Charles has $795,000, withdraws $51,600/year at 6 percent. n = 44.3 years - to age 112. He can safely increase spending by $8,000 to $10,000/year.
Example 2: Deborah, 71, Reassessing After a Market Decline
Portfolio dropped to $490,000. Withdraws $38,000/year at 5.5 percent. n = 23.1 years (to age 94). Reducing to $32,000: n = 34.5 years. A $6,000 annual spending reduction extends the portfolio by 11+ years.
Example 3: The Hendersons, 62, Planning Pre-Social Security Withdrawals
$1,180,000 portfolio, $94,000/year expenses. They delay Social Security to 70. After 8 years of full withdrawals, portfolio: $950,319. From age 70 with Social Security: withdrawal drops to $37,600/year. Return exceeds withdrawal - portfolio never depletes.
Common Mistakes to Avoid
- Calculating depletion based on total expenses rather than portfolio withdrawal.
- Assuming a constant return each year.
- Not accounting for inflation in the withdrawal amount.
- Ignoring Required Minimum Distributions.
- Using a single optimistic return assumption without stress-testing.
- Treating the depletion year as an acceptable endpoint.
- Not modeling what happens after Social Security begins.
Final Thoughts
Run your own withdrawal longevity analysis today at https://www.calcadvisor.com/calculators/retirement-withdrawal-calculator.