Generally, an 8oz cup of oolong tea yields about 1/3 less than that of an 8oz cup of coffee. This measurement varies depending on how long the tea is steeped. The longer the steep time, the higher the caffeine content will be. Caffeine content will lessen each time tea is re-steeped. In the case of oolong teas, the caffeine content lessens by about 1/3 with each steeping.