What this tool does and doesn't do
This calculator compares how broad asset-class mixes have historically behaved. It is an educational illustration, not investment advice, and deliberately describes whole categories — stocks and bonds — rather than recommending any specific fund, security, or provider.
It also does not tell you which risk level to choose, because that genuinely depends on things a calculator cannot see: your job security, your other assets, your obligations, and how you would react to watching your balance fall by a third. For decisions about your own money, a licensed financial adviser can consider all of that. What this tool can do is make the tradeoff concrete.
One deliberate design choice: it shows a range rather than a single number. Any tool that projects one confident figure for a stock portfolio thirty years out is presenting a guess as a fact.
Risk and return are the same decision
The central fact of investing is that higher expected returns are compensation for accepting worse outcomes along the way. You cannot select the return without also selecting the risk.
Move from a conservative 20/80 mix to an all-stock portfolio and the assumed long-run return roughly doubles. So does the volatility, and the worst historical year goes from about −10% to roughly −43%. That −43% is not hypothetical: it is approximately what a US stock portfolio did between late 2007 and early 2009.
This is why the calculator translates the worst historical year into dollars against your projected balance. A 27% loss is an abstraction; watching $105,000 disappear from a $390,000 balance in twelve months is the actual experience. If that number would make you sell, the mix is too aggressive — and selling at the bottom is what converts a temporary decline into a permanent loss.
Time horizon changes everything
The single most important input here is not risk tolerance but time. Volatility in any one year is largely unpredictable, but the range of *annualised* returns narrows as the horizon lengthens — roughly with the square root of the number of years.
Practically, that means a 60/40 portfolio over twenty years produces a much tighter band of outcomes than the same portfolio over three years. Long horizons are what make stock exposure reasonable; short horizons are what make it dangerous.
The common framing is to match the mix to when you need the money. Money needed within two or three years generally does not belong in the market at all. Money needed in thirty years arguably should not sit in cash, where inflation erodes it with near-certainty.
The assumptions behind the numbers
The return, volatility, and worst-year figures are drawn from widely published long-run US market history. Three caveats apply, and they matter.
First, US markets during the twentieth century were unusually strong by international standards. Studies of other developed markets produce lower safe withdrawal rates and lower average returns. Assuming the US future resembles the US past is an assumption, not a law.
Second, these are averages over very long periods. Real sequences arrive as clusters of good and bad years, and the order matters enormously once you are withdrawing rather than contributing.
Third, the figures are before fees and taxes. An expense ratio of 1% instead of 0.05% can consume roughly a fifth of your final balance over thirty years — an effect comparable to shifting your entire allocation, achieved through a line item most people never look at.
Frequently asked questions
- Which risk level should I choose?
- That depends on your timeline, your job stability, your other assets, and your genuine reaction to losses — which is why this tool compares options rather than recommending one. A common starting framework is more stock exposure for longer horizons and less as you approach needing the money. For your specific circumstances, speak to a licensed financial adviser.
- Why show a range instead of one number?
- Because a single number implies a precision that does not exist. Roughly two thirds of historical outcomes fall within the band shown, which means a third fall outside it — in both directions.
- What's the difference between stocks and bonds here?
- Stocks represent ownership in companies: higher long-run returns, much larger swings. Bonds are loans to governments or companies: lower returns, far more stable, and they have historically held up better when stocks fall. The mix between them is the main lever on portfolio risk.
- Does this account for fees and taxes?
- No. Both meaningfully reduce real-world results. Subtract your funds' expense ratios from the assumed return, and remember that gains outside tax-advantaged accounts are taxable.