On a certificate of analysis, the "THC" line does not tell the whole story. Two values almost always appear side by side: delta-9-THC (the neutral form) and THCA (its acid form). Mixing them up leads you to underestimate how much THC a product really contains.
Two forms of the same molecule
In the raw plant, THC exists mainly in its acid form, THCA. When exposed to heat (burning, vaporizing, heating) or over time, part of the THCA converts into delta-9-THC. The lab therefore measures the two forms separately, then calculates a sum.
The total THC formula
Total THC = delta-9-THC + (0.877 × THCA)
The 0.877 factor accounts for the difference in mass between the acid form and the neutral form. Reputable reports state this calculation rule themselves at the bottom of the page.
A worked example
- Product A: delta-9-THC 0.08%, THCA 0.06%. Total THC: 0.08 + (0.877 × 0.06) = 0.13%.
- Product B: delta-9-THC 0.20%, THCA 0.50%. Total THC: 0.20 + (0.877 × 0.50) = 0.64%.
Product B shows "0.20% delta-9-THC", which looks lower than 0.3%. Its total THC, however, is above 0.3%. That is why a single figure on its own is not enough.
To run this calculation with the values from your own certificate, use our total THC calculator.
Which limit, which value?
Depending on the country and the legislation, the 0.3% limit (or 0.2%) may apply to THC alone or to total THC. We do not decide this for you: the applicable rule should always be checked with the authorities in your country.
What we display
Where the analysis report allows it, we use total THC (not delta-9-THC alone). If this total THC is above 0.3%, the product page flags it. See the methodology page for details of how the score is calculated.
What to check on your certificate
- Both the THC and THCA rows are present (not just "THC").
- A "total THC" row or the calculation formula is shown.
- The limit of quantification is stated (for example 0.01%): "not detected" means "below this limit", not "zero".
- The measurement uncertainty is given: a result close to the legal limit leaves little margin.
For the other points to check on a report (lab, batch, date, method), see our guide How to read a CBD certificate of analysis.
This site makes no health claims. This information does not constitute legal advice. Hemp products not intended for use as food, for adults only.