Total THC

Total THC is a calculated figure that combines delta-9 THC with the portion of THCA that would convert to THC when heated, using a factor of 0.877.

Raw hemp contains most of its THC as the acid THCA, which is not intoxicating but decarboxylates to delta-9 THC with heat or time. The conversion factor accounts for the carbon dioxide lost in that reaction, so total THC equals delta-9 THC plus 0.877 times THCA. Federal hemp production rules use total THC to judge whether a crop meets the 0.3 percent definition.

On a certificate of analysis, total THC appears in the cannabinoid section alongside the individual delta-9 THC and THCA lines, and it is the stricter of the available measures because it cannot be lowered simply by leaving the acid form unconverted. Products described as 0.0% THC should show that figure on the total THC line, not only on the delta-9 line, with the reporting limit printed beside it. Comparing the total line across certificates from different laboratories requires checking that they used the same calculation.