Total THC is the figure most labels use to describe how strong flower or a concentrate is. It combines two numbers from the lab report: the THCA, which is the inactive acid form, and the delta-9 THC, which is already active.
The formula is: total THC = (THCA × 0.877) + delta-9 THC. The 0.877 factor exists because when THCA is heated it loses a carboxyl group, which makes up about 12.3% of the molecule's weight. So 20% THCA can become roughly 17.5% THC.
Here is a quick example. A lab report shows 24.0% THCA and 0.6% delta-9 THC. Total THC = 24.0 × 0.877 + 0.6 = 21.6%. That 21.6% is the number you would compare against other products.
Some labels show "THC" alone or list THCA without converting it, which can make a product look stronger than it is. When in doubt, look at the COA and do the math yourself, or ask staff.
Total THC is also only one part of the picture. Two flowers with the same total THC can feel and taste different because of their terpene content, freshness and your own tolerance. Use the number to compare, not as the only measure of quality.