Based on the relationship between formation pressure and minimum horizontal stress, as well as the low leak-off rate and abnormal high reservoir pressure commonly observed in tight sand, the authors devised a new method to calculate the reservoir pressure in tight sand using the pre-frac test. Numerous methods have been published to calculate reservoir pressure using pre-frac test. However, all of them require extended pre-frac testing time, taking hours in conventional formation while days in tight sand. It is not practically viable to keep the frac crew waiting so long before a frac can be executed. In contrast, this new method uses the information collected from a 5-minute pre-frac test, which is standard routine for fracs in the Denver-Julesburg basin (DJ basin). Furthermore, this new method has been validated by the conventional well tests conducted by several service companies.