How the calculation works
The calculator repeats the same step for every month, for up to 100 years.
Balance after the month = (balance − withdrawal) × (1 + monthly return)
Monthly return = (1 + yearly return)1/12 − 1
The withdrawal is multiplied by 1 plus inflation once a year. Savings have run out when the balance cannot cover the next withdrawal.Worked example
100,000 in savings, 1,000 a month, 0% return and 0% inflation.
- There is no return, so the balance falls by 1,000 each month.
- 100,000 ÷ 1,000 = 100 months.
- Your savings last 8 years and 4 months.
What this calculator does not include
- Changing returns. Real markets go up and down, and the order of good and bad years matters.
- Taxes, fees, pensions or other income.
- Extra withdrawals or deposits along the way.
Amounts are rounded for display only; the calculation itself is not rounded. Results are estimates for information, not financial advice. Last updated: 12 November 2026.
Frequently asked questions
How does this calculator work?
It goes through your savings month by month. Each month it takes out your withdrawal, then adds the return on what is left. When the money cannot cover a withdrawal any more, your savings have run out.
Why does the amount rise with inflation?
Prices go up, so the same amount buys less each year. If you want to keep your spending power, the withdrawal has to rise too. Enter 0% inflation to keep it fixed.
What return should I use?
Use a cautious number after costs and taxes. Real returns change from year to year, and a bad start right when you begin withdrawing can hurt a lot. Try a lower return too to see how sensitive the result is.
What does "more than 100 years" mean?
The return is high enough compared with the withdrawal that your savings are not used up within 100 years. It does not mean the plan is safe, only that the model does not run out.
Can I find a monthly amount that lasts a set time?
Yes. Choose "Monthly amount for a set time", enter the number of years, and the calculator finds the largest monthly withdrawal that lasts exactly that long.