How it works
This calculator answers one narrow question: for a given age and a given appetite for risk, what share of a portfolio belongs in stocks and what share in bonds? It deliberately ignores your income, your mortgage, your pension and your net worth, because an age-based glidepath has no way to see any of them. What it does is apply one published heuristic consistently, so the number it returns is reproducible and you can see exactly which input moved it. The rule implemented here is the Rule of 110: stock percentage = 110 minus age. A 35-year-old therefore gets 110 − 35 = 75% stocks, with the remaining 25% in bonds. Risk tolerance then shifts that figure by a fixed number of points rather than by a percentage. Choosing *conservative* subtracts 15 points, *moderate* leaves the figure untouched, and *aggressive* adds 10. The same 35-year-old lands at 60/40 on conservative and 85/15 on aggressive, so the risk selector is worth 25 percentage points of equity exposure across its full range — a bigger swing than five years of ageing produces. The result is then clamped to the range 10%–100%, and the clamp genuinely bites at the edges rather than being decorative: an 18-year-old on aggressive computes 110 − 18 + 10 = 102 and is reported as 100% stocks / 0% bonds, while an 80-year-old on conservative computes 30 − 15 = 15 and is reported as 15/85. International exposure is reported as a share of the stock sleeve, not of the whole portfolio, which is the single most common misreading of this tool. The calculator takes 30% of the stock figure and rounds it, so 75% stocks produces 23% international — and 23% of the equity sleeve is 23% × 75% = 17.25% of the total portfolio, not 23% of it. The suggested-fund line is driven entirely by the stock figure: at 80% or above the tool points to a total-market index fund plus an international index fund, from 50% to 79% to a stock index, bond index and international fund, and below 50% to a balanced fund or a three-fund portfolio. Worked example on the defaults, which are age 35, moderate risk and a $100,000 portfolio. Stock allocation = 110 − 35 = 75%. Bonds = 100 − 75 = 25%. International = round(75 × 0.30) = 23% of stocks. In dollars that is $75,000 in stock funds and $25,000 in bond funds; inside the $75,000 equity sleeve, 0.23 × $75,000 = $17,250 is international and $57,750 is domestic. Two things the output does not tell you, and both matter more than the last few points of precision. The Rule of 110 is a heuristic, not a research finding, and the study most often cited in its defence is routinely misquoted: Brinson, Hood and Beebower found in 1986 that asset allocation policy explained roughly 93% of the *time-series variation* in a single fund’s quarterly returns, not 93% of the *difference in returns between one portfolio and another*. The second is human capital. A tenured teacher with a defined-benefit pension holds bond-like income and can sensibly run more equity than the age rule suggests; a commission-only salesperson holds equity-like income and should run less. The SEC publishes a plain-language introduction to allocation, diversification and rebalancing at investor.gov, and it is worth reading before you treat any single age rule as an answer. Finally, the account you hold each asset in changes the after-tax result: with 2026 contribution limits of $24,500 for a 401(k) and $7,500 for an IRA (IRS), holding the bond sleeve inside a tax-deferred account and the equity index funds in a taxable account is usually worth more than fine-tuning the split itself.
Formula
Stock % = clamp(110 − Age + risk adjustment, 10, 100)
risk adjustment: conservative −15 moderate 0 aggressive +10
Bonds % = 100 − Stock %
International % (share of the STOCK sleeve) = round(Stock % × 0.30)
Fund suggestion
Stock % ≥ 80 → total-market index + international index
Stock % 50–79 → stock index + bond index + international
Stock % < 50 → balanced fund or three-fund portfolio
Worked example — age 35, moderate, $100,000
Stock % = clamp(110 − 35 + 0, 10, 100) = 75%
Bonds % = 100 − 75 = 25%
Intl % = round(75 × 0.30) = 23% of the equity sleeve
$ stocks = 0.75 × $100,000 = $75,000
$ bonds = 0.25 × $100,000 = $25,000
$ intl = 0.23 × $75,000 = $17,250 (= 17.25% of the portfolio)
Tips
- Run the age rule on the whole household balance sheet first, then map it back into accounts. A defined-benefit pension or a very stable government salary is bond-like, so the investable accounts can carry more equity than the age figure alone implies.
- Rebalance on a 5-percentage-point band rather than on the calendar alone. Bands trade less than a fixed annual reset and they catch the drift that actually matters.
- Rebalance with new contributions before selling anything. In a taxable account that avoids realising a gain at all, which is the whole point of holding a target allocation in the first place.
- Re-run the calculation every birthday and again after any change to the pension, the mortgage or the retirement date. The age input is a proxy for time horizon, so anything that changes the horizon changes the answer.
Frequently asked questions
- Why does this calculator use 110 rather than 100?
- The older Rule of 100 (stocks = 100 − age) was written when retirement lasted roughly a decade and bond yields were high enough to fund it. Longer retirements and structurally lower real yields both argue for carrying more equity for longer, which is why the Rule of 110 is the common modern version and why target-date funds hold equity well past the retirement date. At 35 the difference is 10 percentage points of equity: 65/35 under the Rule of 100 versus 75/25 here. Neither number is a law of nature — they are conventions, and the tool simply makes the convention it uses explicit.
- Is the international figure 23% of my portfolio or 23% of my stocks?
- Of your stocks. The output is labelled "International (of stock allocation)" and it is computed as 30% of the stock figure. At 75% stocks that is 23% of the equity sleeve, which is 0.23 × 75% = 17.25% of the total portfolio. If you want 23% of the entire portfolio in international funds you would need to set the stock allocation to roughly 77% and put all of the international holding at 30% of that — or simply add international to your target yourself. The distinction matters when you are placing trades.
- What happens at the youngest and oldest ages the tool accepts?
- The stock figure is clamped to the range 10% to 100%. An 18-year-old on aggressive computes 110 − 18 + 10 = 102 and is reported as 100% stocks and 0% bonds, so the tool will not suggest a leveraged position. An 80-year-old on conservative computes 110 − 80 − 15 = 15 and is reported as 15% stocks and 85% bonds, which is the floor rather than going negative. Both clamps are deliberate: the heuristic is only defensible inside that range, so the tool refuses to extrapolate past it.
- Does the calculator account for Social Security, a pension or a paid-off mortgage?
- No. It sees three inputs — age, risk tolerance and portfolio size — and portfolio size does not even change the percentages, only the dollar figures you can derive from them. A pension, Social Security and a paid-off mortgage all reduce the amount of income the portfolio has to replace, which is economically similar to holding more bonds. The practical way to use the tool in that situation is to decide how much bond-like income you already have outside the portfolio, then choose the risk setting that produces the equity exposure you actually want rather than the one that matches the label.
- How often should I rebalance back to this target?
- A common approach is an annual check plus a 5-percentage-point tolerance band, rebalancing only when the allocation drifts outside the band. In a $100,000 portfolio that means acting when the equity share moves to 80/20 or 70/30 rather than on a fixed date. Bands tend to trade less than calendar rebalancing and they respond to genuine drift rather than to noise. Whichever rule you pick, write it down before you need it — rebalancing decisions made in a falling market are the hardest ones to make well.
- Should I hold the bond portion in my 401(k) or in a taxable account?
- Generally in a tax-deferred account. Bond interest is taxed as ordinary income, while broad equity index funds distribute little and what they do distribute is usually qualified. Putting the bond sleeve inside the 401(k) or a traditional IRA and holding the equity index funds in the taxable account lets the tax-inefficient asset sit in the shelter. The 2026 limits are $24,500 for a 401(k) with an additional $8,000 catch-up at 50 or over, and $7,500 for an IRA with a $1,100 catch-up, so there is usually room to execute the split. Asset location is a second-order decision, but it is not a negligible one over thirty years.
- My target says 75% stocks but I am nervous about a crash. What should I do?
- Lower the risk setting rather than ignoring the output, and then write down the number you chose. A 60/40 allocation you can hold through a 35% drawdown beats a 90/10 allocation you abandon at the bottom, because the second one converts a temporary paper loss into a permanent one. The tool models no crash, no sequence risk and no behaviour at all — it produces a target, and the target only works if you can hold it. If the honest answer is that you would sell in a downturn, the conservative setting is the more accurate description of your risk tolerance, not a compromise.