Canadians spent about C$6bn ($5.6bn, £3.5bn) on cannabis in 2015 - almost as much as they did on wine.
The estimate comes from Canada's bureau of statistics, which studied marijuana consumption between 1960 and 2015.
The government has promised to research the drug's effect on the economy and society as it ramps up its plans to legalise cannabis next summer.
The report also found that use has gone up over the years as it has become more popular with adults.
In the 1960s and 1970s cannabis was primarily consumed by young people, according to Statistics Canada.
But in 2015, only 6% of cannabis users were between between 15 and 17 years old, while two thirds of users were over 25.
Canadians consumed about 697.5 tonnes of pot in 2015, which the report estimated to be worth between C$5.0bn to C$6.2bn.
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Since marijuana is not legal yet, the researchers had to estimate its market value, pegging it between C$7.14 to C$8.84 a gram.
Many Canadian provinces have discussed charging about $10 a gram for cannabis once it is legalised. The government's plan, which has been championed by Prime Minister Justin Trudeau, would legalise marijuana consumption throughout the country but leave its method of sale up to the provinces.
In November, the federal government said it planned to levy a 10% excise tax of C$1 per gram of the final retail price, whichever is higher. The provinces will take home 75% of those revenues.
Under that scheme, the government could stand to rake in almost C$700m a year, if Statistics Canada's estimate proves correct.