How Total THC Is Calculated (And Why It Matters)
When you're shopping for THCA flower or edibles, you probably notice the big number on the label: 26%, 28%, even 30%. Most people assume that's the amount of THC they'll experience. But there's a little more chemistry involved. That number is usually based on something called Total THC.
So what is Total THC, and why should you care?
It Starts with THCA
Most of the THC in raw cannabis flower isn’t actually THC—it's THCA (tetrahydrocannabinolic acid), the non-psychoactive precursor to Delta-9 THC. THCA becomes Delta-9 THC when it’s heated through smoking, vaping, or cooking. This process is called decarboxylation.
Because of that, lab reports (COAs) don't just show Delta-9 THC; they also show THCA. And to estimate how much psychoactive THC you'll get after heating the flower, we use this standard formula:
Total THC = (THCA × 0.877) + Delta-9 THC
This reflects the loss in molecular weight that occurs when THCA is converted to Delta-9 THC. The 0.877 factor accounts for that change.
Some people round it to 0.85 for simplicity, but 0.877 is more accurate.
Why We Focus on THCA in North Carolina
In legal cannabis states, flower might contain a mix of THCA and Delta-9 THC—sometimes evenly split. But in North Carolina, hemp laws require that Delta-9 THC remain under 0.3%. So THCA is doing all the heavy lifting.
That’s why, at PhenomWell, we focus on high-THCA flower. When you see a flower with 28% THCA and 0.2% Delta-9 THC, it’s going to feel strong—because you’re essentially getting 24%+ activated THC when you light it up.
What About Edibles?
For edibles, manufacturers decarboxylate the cannabis during processing. That means they use the actual Delta-9 THC number on the label. So when a gummy says it contains 10mg THC, it means active THC, not THCA.
How to Read a COA
Most Certificates of Analysis will show:
- THCA %
- Delta-9 THC %
- (Sometimes) Total THC
- Additional cannabinoids and terpenes
Here’s a real example from our Blue Andez strain:
THCA: 32.04%
Delta-9 THC: 0.05%
Total THC (calculated): (32.04 × 0.877) + 0.05 = 28.13%
This comes directly from a recent COA issued by FESA Labs and matches the lab-verified results we make available in-store and online.
When you're looking at flower with over 30% THCA and compliant Delta-9 THC levels, you’re in top-shelf territory—and you can expect strong, clean effects when it’s smoked or vaped.
If you're trying to understand the true potency of your flower, this formula is your friend.
Final Thought
High-THCA flower is the legal hemp world’s answer to high-THC cannabis. And knowing how Total THC is calculated helps you get a better sense of what you’re really buying.
We know it can feel like a lot of numbers—but we’re always happy to walk you through a COA, explain the differences, or help you find a strain that fits what you’re looking for—especially if you’re comparing products from legal states and wondering what makes ours different.