Retirement calculator: will your savings last?
Enter your savings, how much you plan to spend each year and for how long. The calculator runs 2,000 simulations on real stock and bond returns, shows the chance that the money lasts and finds the yearly spending with a 90% success rate.
- Chance the money lasts
- 95%
- Withdrawal rate
- 4.0%
- Spending with 90% success
- $45,037 / yr
- Median left at the end
- $1.8M
In 95% of 2,000 simulations the savings lasted 30 years. When the money ran out, it happened after 25 years in the median case and after 15 years at the earliest. In a bad case (1 in 10) $267k was left at the end, in a good case (9 in 10) $4.8M, in today’s money.
Historical mode: 12-month blocks drawn at random from the monthly total returns of the S&P 500 (SPY) and US investment-grade bonds (AGG) from 2006-11 to 2026-10, in US dollars, so the crises in that period are part of the draws. Spending is taken at the start of each month and rises with inflation; the portfolio is rebalanced monthly. Taxes are not included. An educational simulation, not a forecast and not financial advice.
How to read the result
The chance of success is the share of simulations in which the savings lasted the whole period. Around 90% or more is a common comfort level for planning; below 75% the plan relies heavily on markets being kind.
The chart follows savings in today’s money: the median path, a bad case that only one simulation in ten did worse than, and a good case. The gap between them is the sequence-of-returns risk: the same average return can end very differently depending on when the bad years arrive.
Changing the stock share, the spending or the horizon and watching the success rate is the most useful way to use the calculator.
Questions
What is a Monte Carlo retirement calculator?
It runs thousands of possible futures for your savings, each with a different sequence of market returns, and counts in how many the money lasts as long as you need it. The share of successful paths is the chance of success; the spread of outcomes shows how much depends on the order in which good and bad years arrive.
Where do the returns come from?
In historical mode the calculator draws blocks of 12 consecutive months at random from the real monthly total returns of the S&P 500 (SPY) and of US investment-grade bonds (AGG), so stock and bond returns stay paired as they really happened, crises included. In assumptions mode you set the average returns and volatilities yourself.
What is the 4% rule?
A rule of thumb from US studies of the 1990s: withdrawing 4% of the starting portfolio in the first year and then raising the amount with inflation lasted at least 30 years in almost every historical period for a stock and bond portfolio. It is a starting point, not a guarantee: it depends on the period studied, on fees and taxes, and on how long retirement lasts.
What does "spending with 90% success" mean?
It is the highest yearly spending, in today’s money, for which at least 90% of the simulations still had money left at the end of the period, with your savings, horizon, allocation, inflation and fees. It is a simulation result, not a safe amount.
What does the calculator leave out?
Taxes, pensions and other income, changes in spending over time, and currency effects for investors outside the US. Past returns, even reshuffled, do not cover every future scenario. Use the result to compare choices, not as a plan.
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Source: MarketStack end-of-day prices, total return with dividends reinvested. Figures are historical and descriptive; they are not forecasts and not investment advice. MEDGE Capital does not recommend buying or selling any instrument. Risk disclaimer.