in 2008 The number of marijuana smokers in the US was calculated at 102,404,000 users. This number was up by 2 million users from 2007. Most of this increase in use was with people in there 40s. The number of frequent users (more than 100 days a year) went up by about 22.5 million...the only problem with this study is that it's probably significantly under calculated. this 102,404,000 users fell into a group of people that were 12 and older, answered the door, and admitted to a complete stranger that they broke state or federal laws. So what is the real number of pot use in America? Nobody can know for sure because of it's legality, but I'd put my money on it being close to 3/4 of the population.