Before you invest heavily in equity allocation or debt funds asset calculation, keep in mind this thumb rule for asset allocation—your risk exposure has to decrease as your age increases. Your equity allocation has to come down as you grow older. Equity allocation is a popular strategy because it allows you to invest in equity funds that offer high returns. However, it also presents high risk. The thumb rule for asset allocation is to deduct your current age from 100. For instance, a 25-year-old investor can invest 75% funds in equity, while a 35-year-old should not invest more than 65% in high-risk equities.