Asset Allocation Calculator

The "100 minus your age" heuristic, and how risk tolerance shifts it

"100 minus your age" is a long-standing, widely-cited shorthand for a starting equity allocation: the younger you are, the more of a portfolio conventionally sits in equities, on the reasoning that there's more time to ride out volatility before the money is needed. This calculator starts from that base, then shifts the equity share by 15 percentage points in either direction depending on the risk tolerance you select — down for conservative, unchanged for balanced, up for aggressive — before splitting what's left between fixed income and a small cash buffer.

It's a simplified rule of thumb, not a model of your actual circumstances. It takes no account of your goals, income stability, other assets, or time horizon — all of which a real allocation decision should weigh. As the calculator states, this is a starting point for a conversation, not a personalised recommendation, and it isn't investment advice.

How the risk-tolerance adjustment works

The resulting equity share is always held between 10% and 90%, and the cash buffer between 5% and 20%, whatever age or risk tolerance is entered — this is the calculator's own built-in heuristic, not a statutory or market figure.

Worked example: two different starting points

At the calculator's own defaults — age 35, balanced risk tolerance — the equity share starts at 100 minus 35, or 65%, and balanced applies no shift. The cash buffer comes out at 10%, leaving 25% in fixed income: a 65% / 25% / 10% split.

Change the inputs to age 60 with a conservative risk tolerance, and the picture shifts on both counts: the age-based equity share of 40% (100 minus 60) is pulled down by a further 15 points to 25%, while the conservative setting raises the cash buffer to 15%, leaving 60% in fixed income — a 25% / 60% / 15% split. The same mechanics, at a different age and a different risk tolerance, produce a noticeably more conservative result.