How likely is it--at your desired spending rate--that your retirement savings will last the remaining years of your life? Retirement sustainability is a calculation that provides an indication of your retirement readiness, and the result informs you of saving and spending adjustments that may be necessary. Retirement sustainability is based on a number of factors such as: how many streams of income you have to support your retirement; your asset allocation nearing and during retirement; your withdrawal rate, and; your longevity risk, which is the risk that you’ll outlive your money during retirement. The calculation differs from firm to firm but is best used as an indicator of whether retirement income adjustments need to be made--be it in asset allocation, diversification, savings or spending rates.