For most of humankind’s history with cannabis, people had no way of knowing how much THC they were getting. The idea of knowing the amount of THC in a joint was a fantasy. There was just “good weed,” “bad weed,” and “okay weed.”

A cannabis enthusiast from 5,000 years ago – or even a few decades ago – would be blown away by the state of the industry today. People aren’t getting much cannabis from nature anymore. It’s not coming from some secretive grow operation either. Today’s hemp and marijuana plants are often grown by leading botanists, and the final products go through thorough scientific tests.

As a result, every legal cannabis product in an in-person or online cannabis dispensary comes with accurate lab results. This includes the THC potency of the product. If you know the cannabinoid concentration of the product, and you know the weight of the product, you can figure out the exact amount of THC in a joint.

Factors Affect the THC in a Joint

When you buy loose flower or a pre-roll, the packaging will likely report some of the official lab results, or contain a QR code that takes you to the lab results online so you can view the information yourself. Those lab results tell you how many milligrams of cannabinoids are in the product.

THC Potency of the Cannabis

Instead of telling you the THC in milligrams, the package and/or the COA will list the cannabinoids as percentages. For example, you might check the cannabinoid and terpene profile and see that a flower offers 18% THCa. When you light the joint and burn the cannabis plant material, that THCa will be decarboxylated and become Delta 9 THC, which produces the “high” effect for which marijuana is known. In other words, you have one piece of the equation to help you figure out exactly how much THC is in a joint.

Amount of Cannabis

Now that you know which percentage of your cannabis is Delta 9 THC (or THCa waiting to become Delta-9), the next factor to consider is how much cannabis you have in total. Multiplying the weight of the cannabis flower by the THC (and THCa) percentage gives you the total amount of Delta 9 THC you can expect once the flower is heated to decarboxylate the THCa.

You’re well on your way to the answer now! You aren’t quite finished yet, though, because there are a few more things to think about. One consideration is whether or not the cannabinoids could have degraded over time.

The Freshness of the Joint

Even if your cannabis has been properly dried and cured, it’s still a plant. Plants degrade a little bit over time. Even if your older cannabis flower or pre-rolled joint is still nice to inhale, it might have lost some of its oomph. More scientifically, it might have lost some of its THC and THCa.

According to some research published by the United Nations, the level of Delta 9 THC in cannabis drops over the course of time:

  • About 17% of the THC in cannabis is gone after one year.
  • 27% of the THC is gone after two years.
  • 35% of the original THC content has been depleted after three years.
  • 41% of the Delta 9 THC is gone from cannabis after four years.

This study covers cannabis stored at room temperature, which is another important consideration. If cannabis is exposed to high temperatures or a lot of direct light, it will probably lose more THC.

The way cannabis is stored and the length of time are both vital to preserving freshness and THC potency. While the data from the United Nations has been carefully collected, the cannabis in your closet or desk drawer won’t degrade at exactly the same rate. You can now make an educated guess about how much THC your flower has lost. Hopefully, you won’t have to worry about this too much because the cannabis will be fresh.

Weed Math: Calculating the THC in a Joint

Now that you know about the variables to consider when estimating the THC in a joint, you’re ready to do some example estimates:

  • Imagine you have a 1-gram (1,000 mg) joint that’s 20% THC and THCa.
    • 1,000 mg of cannabis x 20% THC = 200 mg of THC
  • Imagine you have a 1.2 gram (1,200mg) pre-roll that was 18% THC and THCa, but it’s a year old. Assuming you kept it in the dark at room temperature, it probably lost about 17% of the THC, so 83% of the THC is left.
    • 1,200 mg of cannabis x 18% THC x 83% of THC remaining = 179.28 mg of THC

There’s also a general formula you can use to calculate THC total:

THCtotal = (%THCA) x 0.877 + (%THC)

It helps to have a calculator, but the math is totally doable! That said, there’s still one more thing to think about.

How Much of the THC in the Joint Gets Into Your Bloodstream?

Now you know how much THC is in a joint, but not all of that THC will make it into your bloodstream. As you inhale a joint, some of the smoke goes into the air. Now you’re thinking about your puff technique – how much of the cannabis you get into your lungs and how effectively your body captures the THCa.

This varies so wildly by the person that it’s almost impossible to estimate how much of the THC you’ll actually get. Superefficient smokers might end up processing 50% of the total THC or more. People who puff away more casually might be getting as little as 2% of the total THC.

Final Thoughts: THC in a Joint

Now you know how to come up with a rough idea of how much THC is in a joint. There are many variables, making this more of an estimation than an exact calculation. If you take note of your experiences over time, you’ll be more comfortable accounting for all the above factors.

You’ll also know how to adjust your thinking if you share a joint versus having a personal one. You might find that you get a feel for rolling just the right amount of flower into a joint. On the other hand, you might realize you prefer the consistency of pre-rolls. Cannabis is a personal journey like that.

Buy Cannabis Flower and Pre-Rolls Online

If you have additional questions about the THC in a joint, please don’t hesitate to contact CannaBuddy. We’ll walk you through what you should expect when you buy THCa flower and cannabis pre-rolls online.

Image Source: Dmytro Tyshchenko / Jan Havlicek / Canna Obscura Shutterstock