Combined sales of legal recreational and medical marijuana in the United States is projected to reach more than $8 billion in 2018. That's according to a new report by Marijuana Business Daily citing data from the Marijuana Business Factbook, which forecasts that the 2018 retail marijuana industry could see an estimated $7.4 to $8.2 billion in sales.

The projection is based on sales estimates from the state-legal medical and recreational marijuana markets that already exist, as well as 4-5 additional states that are expected to legalize recreational marijuana and 2-3 states expected to legalize medical marijuana by 2018.

Currently, there are 20 states with legal medical marijuana. Colorado and Washington have both legalized recreational marijuana and about a dozen other states are expected to legalize marijuana in some form in the coming years.

“This total is conservative –- the reality of retail sales could be larger,” Chris Walsh, editor of CannaBusiness Media, the publisher of both the Factbook and Marijuana Business Daily, said in a statement. “Nor does it include wholesale cannabis sales, or the billions of dollars in ancillary cannabusiness revenues such as growing equipment, real estate, legal fees, testing labs, paraphernalia, etc.”

Walsh's suggestion that sales could exceed that $8 billion mark is supported by another recent study that projects that the U.S. marijuana industry could be worth $10 billion by 2018.