The Total THC Formula
Every certificate of analysis on our THCA flower lists THCA and Delta-9 THC as two separate numbers. Total THC combines them into one figure that reflects what the product actually delivers once it’s heated. The formula is:
Total THC = (THCA % × 0.877) + Delta-9 THC %
This isn’t an industry convention someone made up, it’s the literal federal definition. The USDA’s hemp regulations define it directly: “Total THC = (0.877 x THCA) + THC.” Next time you’re checking a batch, you can pull the batch-matched certificate of analysis and run this formula yourself in under a minute.
Why 0.877 Specifically?
The 0.877 isn’t a rounded estimate or a regulatory guess. It comes directly from chemistry.
THCA and THC are almost the same molecule, but THCA carries an extra carboxyl group that THC doesn’t. When heat is applied, that carboxyl group breaks off as carbon dioxide and floats away, a process called decarboxylation. What’s left behind is lighter than what you started with.
THCA has a molecular weight of about 358.5 g/mol, confirmed in the compound record for tetrahydrocannabinolic acid. Delta-9 THC weighs about 314.5 g/mol. Divide one by the other, 314.5 divided by 358.5, and you land on 0.877. That’s the whole story: 0.877 is simply how much of the original molecule’s mass survives the reaction. Nothing about it is arbitrary.
Calculating It Yourself: Three Worked Examples
The math stays the same regardless of potency tier. Here’s how it plays out at three different levels:
Lower-potency flower: A COA shows 18.0% THCA and 0.1% Delta-9 THC. 18.0 × 0.877 = 15.79 15.79 + 0.1 = 15.89% Total THC
Mid-range flower: A COA shows 24.5% THCA and 0.2% Delta-9 THC. 24.5 × 0.877 = 21.49 21.49 + 0.2 = 21.69% Total THC
High-potency flower: A COA shows 31.0% THCA and 0.25% Delta-9 THC. 31.0 × 0.877 = 27.19 27.19 + 0.25 = 27.44% Total THC
Notice the pattern: the higher the THCA number, the bigger the gap between the raw THCA percentage and the real Total THC figure. That gap is exactly what the 0.877 factor accounts for, and it’s why comparing two products on their THCA number alone can be misleading if one has a meaningfully higher starting percentage than the other.
The Formula Isn’t the Same Everywhere
The federal version of this formula only counts Delta-9 THC and its THCA precursor. Some states count more than that.
Ohio is a clear example. State guidance for licensed cannabis products explicitly folds Delta-8 THC into the calculation as well: Delta-9 THC + Delta-8 THC + (0.877 × Delta-9 THCA) = Total THC Content. That’s a genuinely different formula than the federal baseline, not just a stricter limit applied to the same math. A product that passes the federal calculation with room to spare could land somewhere else entirely once a state adds another cannabinoid into the total. If you’re ever comparing potency claims across states, worth reading up on how individual states have handled THCA and total THC before assuming the same formula applies everywhere.
What Total THC Doesn’t Tell You
Total THC is a theoretical ceiling, the maximum you’d get if every bit of THCA converted perfectly and nothing was lost along the way. Real combustion isn’t that clean. Smoking and vaping lose a meaningful share of that potential to heat, side-stream smoke, and simple inefficiency, so the number on the COA is a ceiling to reference, not a promise of exactly what you’ll feel.
That’s the honest way to use this formula: as a way to compare potency between two products on equal footing, not as a literal prediction of your experience. Every product page in our catalog lists Total THC alongside the raw THCA percentage for exactly that reason, so the math is already worked out for you before you buy.
