100 Minus Age Asset Allocation Calculator

The classic rule sets stock allocation at 100 minus age. At 30 that is 70% stocks and 30% bonds; at 60 it is 40% and 60%. Later variants use 110 or 120 minus age, producing a higher equity share at every age. The argument behind them is that retirements have lengthened since the original rule became popular, so a portfolio may need to fund three decades rather than one or two, and a lower equity share across that span carries its own risk of the money running short.

Quick example

With your age of 35, the result is 65.00%.

What's happening under the hood

Stock allocation is 100 minus the age entered, with the remainder in bonds. Because the two always sum to 100, the bond share works out to the age itself. The result rows also show the 110 and 120 variants of the same idea, and all three are clamped so no figure falls below zero or rises above 100%. The rule is arithmetic rather than analysis: it takes one input and ignores income, existing assets, the horizon attached to any particular goal, and how much variation in value the investor can sit through.

Where this fits in planning

This is a "what-if" tool, not a forecast. It helps to test ideas: what happens to the result as you enter different ages. Running several sets of figures shows how sensitive the result is to each input; a single set does not.

Where to go next

This calculation rarely sits alone in a planning exercise. Related tools include the compound interest calculator, the FIRE calculator, and the asset allocation calculator, each answering a different question in the same territory.

Worked example

Suppose you are 45 years old. The formula gives 100 − 45 = 55. This means 55% stocks and 45% bonds. If your portfolio is worth 200,000 in your currency, the allocation becomes 110,000 in stocks and 90,000 in bonds. If you return to the calculator at age 50, the allocation shifts to 50% stocks and 50% bonds on the same portfolio size, which would mean shifting a total of 10,000 from stocks into bonds over those five years to keep pace with the changing rule.

Common situations where this rule appears

• Early-stage retirement planning when a simple starting point is more useful than no starting point
• Discussions about how asset allocation typically evolves across decades
• Educational contexts explaining the relationship between age and risk exposure
• Baseline comparison when evaluating a personalised or professionally designed allocation

What the result shows and does not show

The calculator shows how a single variable, age, produces a theoretical split between two broad asset classes. It does not account for income stability, existing assets, time horizon for specific goals, market conditions, tax environment, or personal risk tolerance. The output is for educational illustration and models one algorithmic approach to a complex decision.