Why Is There No Standard Measurement for Weed?

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Photo: Ricky Beantown/Flickr

The standard definition of a drink may vary wildly from country to country, but in the U.S., at least, the containers you use to deliver the booze to your mouth make it pretty easy to keep track of how much alcohol you’ve consumed. The Centers for Disease Control define a drink as any beverage containing 14 grams of pure alcohol, which roughly translates to the amount found in a single 1.5-ounce shot, a 12-ounce beer, or a five-ounce glass of wine (about a fifth of a bottle). It’ll vary some from drink to drink, sure, but the number of shots you’ve knocked back is a pretty reliable barometer for the amount of alcohol in your system.

Marijuana, on the other hand, has no such handy shortcut, meaning that depending on the level of THC in a joint, a few hits — and even a “hit” can’t be fully standardized — can leave a person unaffected, pleasantly buzzed, completely stoned, or anywhere in between.

“Recommended units in alcohol is rife with problems, but at least it gives you a means to compare a shot of tequila with a pint of ale,” George McBride, a policy officer at the British drug-policy think tank the Beckley Foundation, told Motherboard’s Gabe Stutman last week. “Cannabis users have no way to compare a dab with a joint.”

Earlier this month, Stutman reported, public-health and drug-policy experts gathered at NYU’s Cannabis Science and Policy Summit to talk about the possibility of standardizing a single unit of marijuana. The nature of weed itself, though, makes it a difficult prospect:

The most important factor in determining the potency or psychoactivity of any given quantity of weed is its mass of THC, measured in milligrams. Generally 10 milligrams is considered one dose in both recreational and medicinal uses—however the manner in which it is ingested, say via edible, smoke or vape, can alter the effects, McBride said.

Complicating matters, weed strains can range in potency from today’s average of around 20 percent THC, to over 30 percent. This represents a stark contrast to the weed of the 1980s, which averaged around 4 percent THC concentration. So basically taking “one hit” today is a pretty opaque unit of measurement.

Measuring THC content is easiest in edibles, but even then, there’s no guarantee that a label will accurately reflect the contents. As Stutman noted, a Denver Post report from 2014 found that the THC concentration listed by the manufacturer can be way off base in either direction. A marijuana breathalyzer is also in the works, but some researchers are doubtful that it’ll be accurate enough to prove useful.

“Understanding your dose is essential,” McBride said — but for now, there isn’t much for consumers to go on. In the meantime, four states and Washington, D.C., have already legalized recreational weed, and 20 more are set to have legalization measures on the ballot in November. That’s an awful lot of people with no way to measure how high they’re getting — and, presumably, a lot who will be begging their friends to call an ambulance because, oh my God, they’re positive they’re dying.