Retirement Drawdown Calculator
Saving for retirement is only half the story — the other half is making it last. This calculator answers the question that keeps retirees up at night: how long will my savings hold out at my planned withdrawal rate, and what amount could last indefinitely?
How this calculator works
Each month your balance earns a return and you withdraw a fixed amount. Whether the money lasts comes down to a simple race between growth and withdrawals. If your monthly withdrawal W is less than the growth on your balance (P × r, where r is the monthly return), the principal is never touched and the savings last indefinitely.
Otherwise the balance draws down, and the number of months n until it reaches zero is:
n = ln( W ÷ (W − P · r) ) ÷ ln(1 + r)
The sustainable withdrawal figure shown is simply the monthly growth on your balance — the most you could take while leaving the principal intact.
Important caveats
This model assumes a steadyreturn, but real markets vary — and a string of poor returns early in retirement (“sequence-of-returns risk”) can drain savings far faster than an average suggests. It also ignores inflation eroding your withdrawal’s buying power, taxes, and other income like Social Security or a pension. Treat the result as a planning guide, and build in a margin of safety.
Learn more
- What Is FIRE? A Beginner's Guide to Financial Independence — Financial Independence, Retire Early explained — the savings-rate math, the 25× rule, the variations, and the honest trade-offs behind the movement.
Frequently asked questions
- What is a safe withdrawal rate?
- A widely cited rule of thumb is the '4% rule' — withdrawing about 4% of your starting balance per year (adjusted for inflation) has historically lasted roughly 30 years. This calculator lets you test your specific numbers rather than rely on a single rule.
- What does 'sustainable withdrawal' mean here?
- It's the monthly amount equal to the growth your balance earns, so you'd be living off returns without spending the principal. Withdraw at or below it and, in this steady-return model, the money lasts indefinitely.
- Why is sequence-of-returns risk important?
- Averages hide order. If the market falls sharply in your first few retirement years while you're withdrawing, you sell more shares at low prices and can run out years earlier than an average-return projection implies. A cash buffer and flexibility help manage this.