A cannabinoid result can be expressed in two ways. As-received (wet basis) divides by the weight of the sample as it arrived, water and all. Dry-weight basis divides by the weight after the water is mathematically removed. Because cured flower holds roughly 8-13% water, the same sample reads 9-15% higher on a dry-weight basis.
In practice
A flower sample at 12% moisture tests 20.0% total THC as received. On dry-weight basis: 20.0 / (1 - 0.12) = 22.7%. Neither number is wrong, but comparing one lab's dry-weight figure with another's as-received figure is comparing different things. Some jurisdictions require one basis or the other; a good COA always states which, and prints the moisture.
Dry-weight result = as-received result / (1 - moisture fraction). Moisture fraction is from a loss-on-drying test, e.g. 0.12 for 12%.
Don't confuse with
- Water activity: a measure of how available the water is, not how much there is.
- Wet (fresh) weight of a harvest: plant weight before drying, a different context.
Myth check
Reporting on dry weight is legitimate when disclosed. Swapping bases without saying so inflates labels. See buyer beware.
A cannabinoid is any compound that binds the body's cannabinoid receptors or shares the typical cannabis terpenophenolic structure; the plant-made ones are phytocannabinoids such as THCA and CBDA.Holding dried cannabis in sealed containers so its moisture declines slowly and evenly over weeks, improving smoothness and aroma.THC (Δ9-tetrahydrocannabinol) is the neutral, decarboxylated cannabinoid mainly responsible for cannabis's reported intoxicating effects; the living plant makes it almost entirely as THCA.A COA (certificate of analysis) is a lab's signed report of what it measured in a specific sample, such as cannabinoids, terpenes, moisture and contaminants, with methods and limits.A 0-1 measure of how freely available the water in a material is; for dried cannabis flower the accepted range is about 0.55-0.65 aw.The weight of cannabis after drying (and usually trimming), the basis growers use for yield; it is typically about 20-25% of trimmed wet weight.Moisture correction converts a lab result from as-received to dry-weight basis using the sample's measured water content, usually from a loss-on-drying test.Potency testing is laboratory measurement of a sample's cannabinoid content, normally by HPLC, reported as % w/w or mg/g for each cannabinoid plus calculated totals.Label inflation is the gap between the potency printed on cannabis packaging and what independent testing finds, a documented, mostly upward bias in retail THC claims.A water activity test measures how much of a sample's water is free to support microbial growth, reported as aw from 0 to 1, with cured flower targeted around 0.55-0.65.
