How much marijuana is in a typical joint? Believe it or not, the question has perplexed experts for years. A new study claims to have an accurate estimate based on federal arrest data, and it’s less than regular users think.

Arriving at a trustworthy estimate is important for many reasons, including informing policy makers, law enforcement officials, health care providers and researchers.

Casual and scientific analyses have yielded a wide range of guesses as to the average contents of a marijuana cigarette, whether purchased or prepared at home.

What is a Joint?

A joint is rolled with cigarette papers and contains only cannabis. You can usually fit up to a gram of weed in a joint. 

What Does a Joint Look Like?

Because there are a variety of rolling papers available for purchase, a joint can look like anything from a white cigarette to a rolled up hundred dollar bill to a 24K stick of gold.  

Joints are typically about the size of a cigarette. 

How to Roll a Joint

Rolling a joint can be tricky. You might have to practice a bit before you get it right. 

First, prepare the cannabis. You should grind your bud to break it up without turning it into powder. 

Second, prepare your rolling filter. You just need a small piece of cardboard for this—a torn off corner of a business card will do the trick. Roll it into a tube and place it on one end of the rolling paper. Make sure you’ve placed it on the paper’s glue strip. You can also purchase a filter in advance. 

Third, gently tap your cannabis onto the rolling paper. Try and keep it in an even line. Make sure that there’s about half an inch of paper left on the end that is opposite of the filter so you can properly close the joint when you’re done.  

Fourth, carefully roll the cannabis into a tube. You’ll have to keep the filter in position while you do this. Lick the glue on the paper and fold it over the tube. 

HOW MANY GRAMS?

The actual average may be much less. The new study, an analysis of federal drug arrest data published in the journal Drug and Alcohol Dependence, found the average amount of weed in a joint to be much smaller than those estimates: just 0.32 grams.

Such estimates about more than better understanding a high. Many users report marijuana consumption in terms of joints smoked, a statistic that is useless to researchers, authorities or policy makers without an accurate approximation of what that means.

“In order to get good projections, you need to be able to turn those answers — ‘I’ve had one joint in the last 30 days’ — into a quantity,” said Greg Ridgeway, a professor of criminology and statistics at the University of Pennsylvania who helped write the study with Beau Kilmer, a director of the RAND Drug Policy Research Center.

“These estimates can be incorporated into drug policy discussions,” the two researchers wrote, “to produce better understanding about illicit marijuana markets, the size of potential legalized marijuana markets, and health and behavior outcomes.”

Their estimate is based on marijuana purchase data collected from interviews with people who were arrested from 2000 to 2003 and from 2007 to 2010 under a Department of Justice program. While the answers came in many forms, Dr. Ridgeway and Dr. Kilmer focused on the more than 10,000 responses in which marijuana was measured in grams, ounces or joints.

The average price per gram, they found, was $6.81; the average joint was $3.50.

They couldn’t stop there. Although dividing the joint price by the gram price yields a rough estimate of a joint’s weight — about half a gram — it ignores how prices vary by location, time and quantity.

Those factors can significantly influence the estimates. Bulk discounts, in particular, modulate price. For example, the average price per gram jumps to $9.30 if the analysis is limited to purchases of five grams or less.

“When people buy an ounce of marijuana, they get a real volume discount,” Dr. Ridgeway said.

To account for those variations, the researchers applied a mathematical drug pricing model to the data, yielding their answer of 0.32 grams in the average joint.

Dr. Kilmer and Dr. Ridgeway acknowledge that their estimate is imperfect. It reflects just one population of marijuana consumer — people who have been arrested — and only in a smattering of counties across the United States.

But it is a convincing measurement nonetheless. Indeed, in 2015 a global drug survey conducted by academics found that most users get about three joints from a single gram of marijuana, or roughly 0.33 grams per joint.

Exactly how much marijuana is in a typical joint may be less than previously thought, a new study finds.

Researchers estimated that the average joint contains 0.32 grams (0.01 ounces) of marijuana. That’s lower than some previous estimates; for example, a 2014 report from the White House on America’s drug use estimated that the average joint has about 0.43 g (0.02 ounces) of marijuana. Other studies have estimated that a typical joint contains as much as 0.75 g (0.03 ounces).

Figuring out precisely how much marijuana is in a typical joint can help researchers answer important questions about drug use and trafficking, the researchers said. [11 Odd Facts About Marijuana]

“It turns out to be a critical number in estimating how much marijuana is being consumed [nationwide], how much [of the drug that] drug-trafficking organizations are putting on the market and how much states might expect in revenue post-legalization” study co-author Greg Ridgeway, an associate professor of criminology and statistics at the University of Pennsylvania, said in a statement.

The new findings are based on information from more than 10,000 marijuana purchases over 11 years. This information comes from a survey of people in the U.S. who were arrested and interviewed about their substance use and drug transactions. When interviewees mentioned that they bought a certain number of joints for a certain price, the researchers used this information to estimate the average grams of marijuana in each joint.

The researchers also used a mathematical model to take into account differences in drug prices in different areas, as well as price inflation over the years.

The new findings “can be incorporated into drug policy discussions to produce better understanding about illicit marijuana markets, the size of potential legalized marijuana markets, and health and behavior outcomes,” the researchers said.