Asset Allocation by Age: Stocks vs Bonds

Short answer: Asset allocation by age is a family of commonly cited formulas, such as 100 or 110 minus your age in stocks, that use age as a rough stand-in for time horizon, shifting a portfolio gradually from stocks toward bonds as a goal gets closer. They are reasonable starting points, not personalized answers, because the real drivers are your actual horizon, your other income, and how you behave when the market falls, none of which a birth year alone can capture.

Ask how to split money between stocks and bonds and the internet hands you a number tied to your age, as though risk were a function of birthdays. It is not, quite. Age is a convenient stand-in for something that actually matters, how many years the money has to recover before you need it, which is why the formulas built around age work reasonably well for most people most of the time, and also why they quietly fail for anyone whose situation does not match the assumption underneath them.

This walkthrough takes the formulas seriously without taking them literally. It covers where the common rules of thumb come from, what they are actually approximating, where a target-date fund automates the whole thing, and where the simple version breaks down, for a retiree with a pension, for an aggressive saver with decades to go, for anyone whose real risk tolerance does not match their calendar age. Every percentage and dollar figure here is illustrative, meant to show the mechanism, never a recommendation for your own portfolio. Run your own numbers in the calculator further down the page.

Why “by age” is really “by time horizon” wearing an age label

The question an allocation formula is actually trying to answer is not how old you are, it is how long the money has before you need it and how much of a decline you could absorb without being forced to sell at a bad time. Age is a convenient, easily available proxy for that, because for a typical retirement saver, time horizon and age move together: a 30 year old is usually decades from needing retirement money, a 65 year old usually is not.

The proxy breaks whenever horizon and age come apart. A 60 year old saving for a goal 20 years out, a second retirement account nobody plans to touch for decades, has a horizon that looks nothing like a typical 60 year old’s. A 35 year old saving for a house down payment in two years has a horizon that looks nothing like a typical 35 year old’s retirement account. In both cases, the honest allocation follows the actual horizon, not the age on the formula.

The core trade-off every formula is approximating

Stocks have historically offered a higher expected long-run return than bonds, compensating investors for tolerating larger and more frequent declines along the way. Bonds offer a lower expected return with a gentler ride. Neither is free: the stock investor is paid, on average, for bearing volatility; the bond investor gives up expected return in exchange for a smoother path.

Time is what lets an investor collect the stock premium without being destroyed by the volatility that comes with it. A severe decline that would be catastrophic to someone who needs the money next year is, for someone with twenty years before they need it, simply a rough patch the portfolio has time to recover from. That is the entire trade-off underneath every age-based allocation formula: more time buys the right to hold more of the asset with the better expected return and the rougher ride, because there is time to ride it out.

The 100, 110, and 120 minus age formulas

The most commonly cited version of the rule says to hold a percentage in stocks equal to 100 minus your age, with the remainder in bonds: a 30 year old holds roughly 70 percent stocks, a 60 year old roughly 40 percent. Variations commonly use 110 or 120 in place of 100, producing a higher stock share at every age, reflecting two commonly cited reasons: longer life expectancies, which lengthen the horizon retirement money actually needs to last, and the observation that many investors have historically carried more stock than the original 100-minus-age formula suggested without obvious harm.

There is no authority that sets these numbers, no regulation behind them, and no guarantee that any of them suits a specific person. They are a starting formula, popularized because they are easy to remember and apply, worth adjusting once you know your own horizon, your own other income, and your own tolerance for watching a balance fall.

What “stocks” and “bonds” mean inside the formula

The two-word shorthand hides real variety on both sides. “Stocks” can mean a broad domestic index, a tilt toward smaller companies, an allocation that includes international markets, or a concentrated position in a handful of names, and these carry meaningfully different risk and return characteristics even though the simple formula treats them as one bucket. “Bonds” similarly spans short-term government debt, long-term corporate debt, and everything between, with very different sensitivity to interest-rate moves.

A formula that says “65 percent stocks” has not actually specified a portfolio until you decide what kind of stocks and in what proportion, which is why two investors following the identical age-based percentage can end up with meaningfully different risk, depending on what sits inside each bucket.

Risk capacity versus risk tolerance: two different inputs

An age-based formula is really trying to estimate risk capacity, the objective ability to absorb a decline without being forced to sell at a bad time, which depends mostly on horizon and on how much other income or savings you have. Risk tolerance is a separate, subjective thing: how much of a decline you can watch happen without abandoning the plan, which depends on temperament as much as on math.

The two do not always agree. An investor with decades of horizon and a stable income has high risk capacity by any formula, but if a 20 percent decline genuinely causes them to sell everything at the bottom, their real-world risk tolerance is lower than the formula assumes, and an allocation that respects their actual behavior, even if it is more conservative than the formula suggests, produces a better real outcome than a theoretically optimal one they cannot hold onto. The reverse happens too: an investor with modest risk capacity but a strong stomach for volatility and other resources to fall back on may reasonably carry more stock than a formula built for the average case would suggest.

A worked example: the same decline at three different ages

Make the mechanism concrete with an illustrative 200,000 dollar portfolio held by three different investors, each following the 110-minus-age formula from the chart above, and each facing the same illustrative 30 percent stock market decline.

At 25, holding 85 percent stocks, 170,000 dollars sits in stocks. A 30 percent decline removes about 51,000 dollars, 25.5 percent of the total portfolio. At 45, holding 65 percent stocks, 130,000 dollars sits in stocks, and the same decline removes about 39,000 dollars, 19.5 percent of the total. At 65, holding 45 percent stocks, 90,000 dollars sits in stocks, and the decline removes about 27,000 dollars, 13.5 percent of the total.

The younger investor loses the most in percentage terms and has the most time to recover it through future contributions and future growth. The older investor loses the least in percentage terms, which matters more at that age because there is less time, and often fewer future contributions, to rebuild a loss before the money is needed. Neither outcome is better in the abstract. Each is matched to how much time stands between the decline and the point the money gets spent.

How a target-date fund automates the whole mechanism

A target-date fund takes this entire glide path and builds it into a single holding, shifting its own stock-to-bond mix on a predetermined schedule as the named year approaches, so an investor who buys the fund and does nothing else is automatically walking down a version of the chart above without placing a single rebalancing trade. Our explainer on target-date funds covers how the glide path and the fees inside one actually work.

The convenience comes with a real assumption worth checking: the fund assumes its glide path is your entire allocation. The moment you also hold a separate brokerage account, an old 401(k) you have not rolled over, or a spouse’s accounts with their own holdings, the fund’s carefully built percentage stops describing your actual household allocation, and the whole mix needs to be looked at together rather than fund by fund.

Why a glide path still needs a check against your own situation

A formula or a target-date fund both assume a fairly typical case: a saver with no other significant income who needs their portfolio to fund most of retirement spending. Two common situations change the right answer meaningfully. A future pension or a strong expectation of a substantial Social Security benefit reduces how much the portfolio alone has to carry, which supports holding more stock for longer than the simple formula suggests, since a guaranteed income floor underneath the portfolio absorbs some of the risk a pure savings-only retiree would have to carry entirely in the allocation itself. Our explainer on what a pension is and our walkthrough on estimating Social Security both feed into this.

The opposite situation, a shortened timeline due to an early retirement plan or a goal that moved closer than expected, argues for shifting toward bonds faster than a standard formula built for a traditional retirement age would suggest. Our walkthrough on retiring at 60 with 500k and our explainer on how long retirement savings last both work through horizon-specific versions of this question.

Sequence-of-returns risk: why the final stretch is different

Average return over a long horizon is not the only thing that matters; the order the returns arrive in matters just as much, especially right around the point withdrawals begin. A severe decline early in retirement, combined with withdrawals being taken from a shrinking balance, can permanently damage a portfolio’s ability to last, even if the average return over the following decades turns out fine. The identical sequence of returns in reverse order, the decline arriving late instead of early, does far less damage, because fewer withdrawals have been taken out of the smaller balance by the time it recovers.

This is the deeper reason the formula shifts a portfolio toward bonds specifically as a goal approaches, rather than only caring about the average mix held over an entire lifetime. The years immediately before and after retirement begins are disproportionately important to get the allocation right, because that is when a bad sequence does the most permanent damage.

The rebalancing mechanism: what keeps the mix on target

A portfolio does not hold still at its target allocation on its own. Stocks and bonds grow at different rates, so after a strong run for stocks, a target of 65 percent stocks can quietly drift to 72 or 75 percent without a single trade being placed, simply because the stock portion grew faster. Rebalancing is the act of selling some of what grew and buying some of what lagged, to bring the mix back to target.

Take an illustrative 200,000 dollar portfolio that drifted from a 65 percent stock target to 75 percent stocks, 150,000 dollars in stocks and 50,000 dollars in bonds, after a strong stretch for stocks. Restoring the 65 percent target means selling about 20,000 dollars of stock and buying about 20,000 dollars of bonds, bringing the mix back to 130,000 dollars in stocks and 70,000 dollars in bonds. Nothing about the dollar amount of the portfolio changed in that trade; only the risk level did, back down to what was originally chosen.

Rebalancing by threshold versus by calendar

Two common approaches decide when to rebalance. A calendar approach rebalances on a fixed schedule, commonly once a year, regardless of how far the mix has drifted. A threshold approach rebalances whenever an allocation moves a set number of percentage points away from its target, regardless of how much time has passed. Both are reasonable, and both beat never rebalancing at all, which lets a portfolio’s risk level drift further from the chosen target the longer it goes unchecked, usually toward more stock after a long stretch of stock gains, which is exactly the wrong direction heading into a decline.

Rebalancing too often adds friction without much benefit: in a taxable account specifically, frequent rebalancing can trigger capital gains taxes on gains that did not need to be realized yet, a cost our comparison of taxable and retirement accounts covers in more depth. Inside a retirement account, where trades do not trigger an immediate tax event, the cost of rebalancing more often is lower, which is one reason many target-date funds rebalance more frequently than an individual investor managing a taxable account typically would.

What goes wrong with a too-conservative allocation early

Holding too much in bonds decades before retirement has a cost that is easy to underweight because it never shows up as a single bad day, only as a long, quiet gap in compounding. Our explainer on compound interest shows how much that gap can widen over decades; a lower expected return compounding for thirty years produces a meaningfully smaller ending balance than a higher expected return compounding over the same stretch, even without any single dramatic event marking the difference.

The usual cause is an understandable but miscalibrated fear of volatility applied to money that will not be needed for decades, where the volatility is genuinely not the risk that matters most. For a young saver, the bigger risk is usually under-saving or holding too conservative a mix, not a temporary decline the portfolio has decades to recover from.

What goes wrong with a too-aggressive allocation late

The mirror-image mistake shows up near or in retirement: an allocation that stayed aggressive out of habit, inertia, or a run of good years that made a high stock share feel comfortable, right as the horizon for a large piece of the portfolio shortened. This is precisely the sequence-of-returns problem from earlier in concrete form, a severe decline arriving with little time to recover and withdrawals already underway, and it is the scenario every glide path is specifically built to reduce the odds of.

International, small-cap, and the slices the simple formula skips

The two-bucket formula is a starting point, not a finished portfolio. Within the stock allocation, many investors hold some mix of domestic and international exposure, and some mix of larger and smaller companies, on the reasoning that diversifying across more of the global market reduces the odds of being overly dependent on any single country’s or company size’s performance. Within the bond allocation, choices about term length and credit quality change how the bond portion actually behaves, which matters because not all bonds respond to the same conditions the same way.

None of this changes the underlying mechanism this walkthrough is built around, matching stock exposure broadly to time horizon, but it is worth knowing the simple age-minus-formula is describing the stock-versus-bond split only, not a complete portfolio specification, and the decisions inside each bucket deserve their own attention rather than being treated as settled by the headline percentage.

A short-term cash bucket near retirement

Some glide paths add a third piece beyond stocks and bonds specifically for the years immediately around retirement: a cash or near-cash reserve sized to cover a year or two, sometimes more, of planned withdrawals. The purpose is narrow and specific. It is not meant to grow, and it is not meant to replace the bond allocation’s role in the broader mix. It exists so that a stock decline arriving right when withdrawals begin does not force a sale of depressed stock holdings to fund this year’s spending, which is the sequence-of-returns problem from earlier in a very concrete, cash-flow form.

The mechanism is straightforward: spend from the cash bucket first during a downturn, giving the stock portion time to recover before any of it has to be sold at a loss, and refill the bucket from stocks or bonds during a year when markets cooperate. A retiree holding an illustrative two years of planned spending in cash, alongside the stock and bond mix a formula like the one in this walkthrough suggests, has effectively added a shock absorber on top of the glide path rather than replacing any part of it.

The tradeoff is real and worth naming rather than ignoring: cash earns little to nothing after inflation, so a larger cash bucket is also a drag on the portfolio’s overall expected return, the same tension that runs through every allocation choice in this walkthrough. A year or two of spending is a commonly discussed range for this purpose; a much larger cash position starts to cost more in foregone growth than the sequence-risk protection is usually worth.

Bonds are not a risk-free parking spot

It is tempting to read “bonds” in a formula as the safe half of the portfolio and stop thinking about it further, and that undersells real risks bonds carry. Bond prices move opposite to interest rates: when rates rise, existing bond prices generally fall, and the size of that move grows with the bond’s duration, a measure of interest-rate sensitivity roughly tied to how long until the bond matures. Bonds also carry inflation risk, since a fixed interest payment buys less if prices rise faster than expected, and for anything below the highest credit quality, a real risk that the issuer does not repay in full.

None of this erases the reason bonds anchor a glide path: they are generally less volatile than stocks over most stretches, and less volatile is a real, useful property even though it is not the same claim as risk-free. Treating the bond side of an allocation as something that requires no further thought is its own kind of mistake, just a quieter one than ignoring stock risk.

A simple three-step framework for building your own allocation

Start from a commonly cited formula as a baseline rather than a verdict, since it gives you a reasonable first number to adjust rather than a blank page. Then adjust for anything that makes your actual horizon or risk capacity differ from a typical case at your age: other guaranteed income that reduces how much the portfolio has to carry, a shortened or lengthened horizon relative to a standard retirement age, or money inside the same account earmarked for a different, nearer-term goal. Finally, adjust down, not up, for your honest risk tolerance if a formula-matched allocation would genuinely cause you to abandon the plan during a decline, since an allocation you cannot hold through a bad year is not actually the safer choice it looks like on paper.

Revisit the result periodically rather than constantly, since the whole point of a formula-based starting point is to avoid re-litigating the decision every time the market moves. A once-a-year look, alongside a broader review of contributions and goals, is usually enough to catch a genuine drift in either your circumstances or your allocation without turning the portfolio into something you are reacting to on a weekly basis.

Why contribution rate usually matters more than allocation

It is worth saying plainly, because allocation gets disproportionate attention relative to its actual effect for most savers: how much you contribute typically moves an ending balance more than fine-tuning the stock-to-bond split does, especially more than a decade or more from the goal. Our walkthrough on how much to save each month and our guide to how much to contribute to a 401(k) both cover the lever that, dollar for dollar, tends to do more work than a few points of allocation shifted one way or the other.

This is not an argument that allocation does not matter, the worked example earlier in this walkthrough showed a meaningful difference in how a decline lands at different ages, it is an argument about where to spend your attention first. A saver agonizing over whether to hold 65 or 70 percent stocks while contributing well below what their budget could support is optimizing the smaller lever while leaving the larger one on the table. Settle on a reasonable allocation using the framework above, then put the greater share of your planning effort into the contribution rate, which is the input you have the most direct control over.

Common mistakes in age-based allocation

The first is treating the formula as a rule rather than a starting point and never adjusting it for a pension, a shortened horizon, or an honestly different risk tolerance. The second is the opposite error, abandoning any formula and chasing whatever allocation performed best recently, which tends to mean buying into whatever already ran up and is now more exposed to a reversal, not less.

The third is confusing “bonds” with “risk-free” and treating the bond portion of a portfolio as needing no further attention. The fourth is letting a portfolio drift for years without rebalancing, so the actual risk level creeps away from the one originally chosen. The fifth is applying the same allocation to every account and every goal a household holds, when money earmarked for a near-term goal inside an otherwise long-horizon account deserves its own, more conservative treatment rather than inheriting the account’s overall mix.

The sixth mistake is comparing a formula-based allocation against whatever a friend, a coworker, or a forum post happens to hold, none of which was built around your horizon, your other income, or your risk tolerance. A conversation like that can surface a genuinely useful question to ask of your own plan, but the specific percentage someone else holds is not evidence that the same percentage suits you, and a lot of allocation anxiety traces back to that comparison rather than to anything actually wrong with the plan already in place.

Pricing your own version

Every percentage in this walkthrough is illustrative, and the useful next step is testing your own numbers against it. The calculator on this page runs the 110-minus-age formula, the illustrative decline, and the rebalancing math from the worked examples above against your own age, balance, and assumed decline size. Our explainer on compound interest covers the growth engine a stock-heavy allocation is trying to capture more of, and our walkthrough on how much to save by 30 covers the companion question of how much is going in, which usually matters more to the ending balance than the allocation percentage does.

If the formula’s number feels wrong once you actually picture living through the illustrative decline shown above, that reaction is useful information, not something to override by force of math alone. An allocation that is theoretically optimal and practically unbearable produces a worse real outcome than a more conservative one you can actually hold through a bad year.

When to bring in a professional

A single retirement account, a fairly typical horizon, and no other major income sources is a reasonable case to work through with a formula and an honest look at your own risk tolerance. A more complex situation, a pension or a spouse’s pension in the mix, multiple accounts with different horizons, a concentrated position in employer stock, or a horizon that is meaningfully shorter or longer than a standard retirement age, benefits from a professional who can look at the whole picture rather than one account at a time.

Our explainer on fiduciary financial advisors covers what to look for in someone whose allocation recommendation is not conflicted by what they are paid to sell. A single conversation, even a paid one-time session rather than an ongoing relationship, is often enough to pressure-test a formula-based allocation against your actual circumstances and catch anything the general case in this walkthrough could not have known to flag.

The bottom line

Asset allocation by age is a family of commonly cited formulas using age as a stand-in for the thing that actually matters, how much time stands between now and when the money is needed, and how much of a decline that time can absorb. The worked example above showed the same illustrative 30 percent decline costing a 25 year old’s portfolio 25.5 percent of its value and a 65 year old’s portfolio only 13.5 percent, under formula-matched allocations, which is the entire mechanism in one comparison. A target-date fund automates the resulting glide path, rebalancing keeps a chosen mix from drifting away from itself, and bonds reduce volatility without eliminating risk entirely. Every percentage and dollar figure here is illustrative, current market conditions and your own circumstances belong in your actual decision, so treat a formula as a starting point to adjust, not a verdict, and run your own numbers through the calculator before settling on a mix.

SumLoft writes about how financial arithmetic behaves, and nothing in this walkthrough is investment advice or a recommendation for any specific allocation. The stock and bond percentages, the illustrative 30 percent decline, the 200,000 dollar portfolio, and every dollar figure built from them were chosen to make a mechanism legible, not to forecast market conditions or to describe a portfolio suited to any particular reader. Investing involves risk, including the possible loss of principal, and diversification does not guarantee a profit or protect against loss. Your own allocation depends on your actual horizon, your other income and savings, your tolerance for a decline, and goals this walkthrough cannot see. Confirm your own situation with a qualified fiduciary financial advisor before choosing or changing an allocation.

Edited by Hamza Hai, MBA · Editor

Hamza Hai is the editor of SumLoft. She holds an MBA and reviews the site's articles against our editorial standards, checking that every figure is labelled for what it is, that nothing is presented as verified fact without a source the reader can check, and that the writing stays useful to a non-specialist.

How we research, write and review · LinkedIn