Asset Allocation Calculator

A simple starting point for a genuinely personal decision

Asset allocation — how a portfolio is split between stocks, bonds, and cash — is one of the most consequential decisions in long-term investing, and it is also one that resists a single universal answer, since the right split depends on factors specific to each individual investor. This calculator provides a reasonable, widely used starting point based on age and stated risk tolerance, which is a sensible baseline to react to and adjust, not a personalized recommendation to follow blindly.

Why the rule shifted from 100 minus age to 110 minus age

The classic version of this age-based heuristic, “100 minus your age equals your stock percentage,” dates from an era when life expectancies were shorter and retirements, correspondingly, were expected to last fewer years. As life expectancies extended and the typical retirement horizon grew longer, many financial planners recognized that a longer investing and spending horizon can generally support a somewhat higher allocation to stocks, since there is more time available to recover from any given market decline.

This shifted the common baseline upward, to 110 or in some cases 120 minus age, reflecting that modern retirements planning for several decades benefit from more growth-oriented exposure than the original, more conservative rule provided.

Why risk tolerance adjusts the baseline in both directions

Age alone does not capture genuine differences in how individual investors experience and respond to market volatility. Two investors of an identical age can have very different reasonable allocations depending on how they would actually behave during a significant market decline — one investor might stay the course calmly through a severe downturn, while another might be tempted to sell at the worst possible moment out of genuine distress.

This calculator’s risk tolerance adjustment shifts the age-based baseline up for investors who identify as more aggressive, reflecting a greater willingness to accept short-term volatility in exchange for potentially higher long-term returns, and down for investors who identify as more conservative, prioritizing stability and reduced volatility even at some cost to expected long-term growth.

What this formula cannot see about your actual financial situation

This calculator works from two inputs only — age and stated risk tolerance — and deliberately does not, and cannot, account for a range of factors that legitimately should influence a real allocation decision. A traditional pension providing guaranteed lifetime income effectively functions like a large bond holding already, which can reasonably support a higher stock allocation in the remaining investable portfolio than the formula alone would suggest. Substantial home equity, an anticipated inheritance, unusually stable or unstable employment income, and existing obligations like supporting dependents all reasonably shift what allocation actually makes sense for a specific person, beyond what age and a single risk-tolerance category can capture.

Why holding zero stocks in retirement is not the “safe” choice it appears to be

A common instinct, particularly for a nervous investor approaching or in retirement, is to eliminate stock exposure entirely to avoid market risk. This intuition, while understandable, overlooks a different risk that an all-cash or all-bond portfolio does not protect against: purchasing power erosion from inflation over what can easily be a 20 to 30 year retirement or longer.

A portfolio with no growth-oriented exposure at all struggles to keep pace with rising costs over that length of time, which means “safe” in the sense of low day-to-day volatility can quietly become “unsafe” in the sense of not lasting as long as needed, or not maintaining the same real purchasing power throughout a lengthy retirement. Most financial planning approaches retain some meaningful stock allocation even well into retirement for exactly this reason.

Treating this as a living target, not a one-time decision

Because the age component of this formula shifts gradually every year, and because genuine changes in circumstances or risk tolerance can occur at any point, revisiting the target allocation periodically — every few years, or whenever something material changes — is more appropriate than setting an allocation once early in an investing career and never reconsidering it again.

Once a target is established or revised, the portfolio rebalancing calculator covers the ongoing maintenance question of what to actually buy and sell to keep the real portfolio aligned with whatever target this calculator, or a more personalized process, has established.