Age-and-risk-based stock, bond, and cash portfolio split

The Classic Age-Based Allocation Rule

A common rule of thumb: stock percentage equals 110 minus your age. A 30-year-old is 80% stocks. A 65-year-old is 45% stocks. The logic: younger investors have longer horizons to ride out market downturns and should accept more volatility for higher expected returns. Older investors approaching or in retirement should reduce volatility to protect near-term spending needs. The calculator uses 110-age as the baseline, adjusted by risk tolerance.

Why 110 Instead of 100

The original rule (100 minus age) dates from an era when life expectancy was lower. With longer retirements and lower bond yields, most modern advisors use 110 or 120 minus age to increase equity exposure. Someone retiring at 65 with 25-30 year retirement horizon needs portfolio growth to outlast inflation. A 35% stock allocation may be too conservative for that horizon. The calculator's formula reflects the modern 110 rule plus risk-tolerance adjustment.

Risk Tolerance Adjustment

The formula: base stock percentage = 110 - age, then adjust ± 20 percentage points based on risk tolerance (1 = very conservative, 10 = very aggressive). A risk-averse 40-year-old might have 60% stocks instead of the baseline 70%. A risk-tolerant 60-year-old might have 70% stocks instead of baseline 50%. Risk tolerance depends on psychological comfort with volatility, financial capacity to absorb losses, and time horizon flexibility. Honest self-assessment beats formulas.

The Bond and Cash Split

The calculator allocates non-stock percentage roughly 75% to bonds and 25% to cash. Emergency funds and near-term spending needs go in cash (high-yield savings, money market). Medium-term needs (2-5 years) and portfolio ballast go in bonds. The specific cash-versus-bond split is less critical than the stock/non-stock split because both are low-volatility components. Adjust cash upward if you have large known upcoming expenses (down payment, tuition) or unstable income.

Worked Example

Age 40, risk tolerance 6 (slightly above average), total portfolio 250,000. Base stock allocation: 110 - 40 = 70%. Risk adjustment: +4 percentage points. Final stock: 74%. Bond allocation: 75% of remaining 26% = 19.5%. Cash: 6.5%. Dollar allocations: 185,000 stocks, 48,750 bonds, 16,250 cash. The calculator returns these numbers directly. Compare with a conservative 40-year-old (risk 3): stock % = 70 - 8 = 62%, bond 28.5%, cash 9.5%.

When Rules of Thumb Break Down

Large fixed incomes (pensions, annuities): effectively act like bonds, reducing required bond allocation in the portfolio. Very high net worth where annual spending is tiny relative to portfolio: stock tolerance can be higher regardless of age. Short-term goals within the portfolio (house down payment in 3 years): that slice should be heavily cash regardless of age. Imminent retirement: tactical bond ladder for first 5-10 years of spending provides sequence-of-returns protection. The calculator is a starting point; refine based on your specific situation.

Target-Date Funds as a Shortcut

If custom-allocating feels like overkill, target-date retirement funds automate the glide path. Pick the fund with your expected retirement year; the fund manager adjusts stock-bond mix over time as you age. Vanguard, Fidelity, Schwab all offer low-cost target-date funds at 0.08-0.15% expense ratio. Not perfectly personalised but removes the rebalancing burden entirely. For investors who will not rebalance reliably, a single target-date fund often outperforms a custom allocation that drifts unrebalanced for years.