Total THC (THCA × 0.877 + Δ9)

Total THC estimates the THC actually delivered when a product is heated: THCA percentage × 0.877, plus the Δ9 THC already present. The 0.877 factor exists because THCA loses mass (a carboxyl group) as it converts. This is the most useful number on a COA and the one most often fudged in marketing — a jar advertising “28% THC” whose COA shows 24% THCA and 0.2% Δ9 actually computes to about 21.2%. We recompute this figure for every product we review, and when the vendor’s advertised number and the recomputed one disagree, the review quotes both.