Cannabis THC Potency 

  • How is THC percentage calculated?

As of 2021, roughly 550 chemical compounds have been discovered in cannabis plants. Over 100 of these compounds have been identified as cannabinoids. Delta-9-tetrahydrocannabinol (THC) is a commonly known cannabinoid that provides the psychoactive effect most users experience. Cannabis plants with a higher percentage of THC affect a users’ moods and awareness. Through decades of research, cannabis cultivators have been able to breed cannabis plant strains to increase cannabinoid percentages.  

Federal and state law have specific regulations regarding how THC is measured and reported. According to the Farm Act of 2018, cannabis plants containing a total of less than or equal to 0.3% THC are legally considered hemp. Hemp containing < 0.3% THC has a minimal psychoactive effect. Materials harvested from hemp plants are crafted into items such as rope, textiles, paper, and CBD health-associated products. 

What does potency on a label mean? 

or the purposes of regulation, potency is defined as the quantity of tetrahydrocannabinol (THC) and tetrahydrocannabinolic acid (THCA) per gram of sample. Testing laboratories provide results that translate to the percentages consumers see on packaging labels. The NM state assigned definition of potency is specifically the THC percentages and not necessarily what end consumers experience as their overall effect of product potency. However, the labeled potency of a product helps to inform the consumer’s expectations.  

Results from tested cannabis products are required for the labeling of all commercial products. Cannabis potency labels are a clear indication of what THC levels were at the time of testing. THC percentage, however, is just one aspect of a consumer’s experience. Even under perfect conditions, cannabinoids degrade slowly from acidic forms to active molecules, and then eventually to cannabinol (CBN). Through this natural process, the percentage of cannabinoids in cannabis products fluctuates over time. 

How is THC Percentage calculated? 

THC percentage is an identifying measurement of how much THC is found within cannabis products like flower, edibles, and topicals. For instance, if a strain of cannabis flower contains 15% THC, this means 15% of the dry weight of the flower is made up of THC. This is equivalent to one gram (1000 mg) of cannabis flower containing about 150 mg of THC.  

To calculate the total THC, the acid form of the cannabinoid is multiplied by the difference in molecular weight between the acidic and non-acidic form. Tetrahydrocannabinol Acid (THCA) is the inactive form of THC found in the raw state of cannabis plant. When THCA is exposed to heat, a chemical change occurs and the psychoactive form of the cannabinoid, tetrahydrocannabinol (THC), is produced.   

How has THC percentage changed overtime? 

Studies show THC potency has slowly increased over the years. This increase can be attributed to various factors, including selective breeding, advancements in cultivation techniques, and the rise of indoor cultivation. Cannabis growers and manufacturers are creating products that are more potent than previous generations have seen.   

In the 1960s, the THC content in cannabis typically ranged from 1-2%. During this time, the growth of cannabis predominantly consisted of landrace strains, which were native varieties found in different parts of the world. Cannabis plants were being harvested and every aspect of the plant was consumed. These strains generally had lower THC levels compared to the modern hybrid strains available today. Modern cannabis cultivators have shifted their focus to only harvesting the flower product of a cannabis plant. By harvesting the most enriched portion of the plant, consumers and cultivators experienced a drastic change in potency and overall effects. In recent studies, researchers found that THC concentrations increased exponentially from 1970 to 2017. The average THC content increased substantially, with many strains surpassing 15% THC and some even exceeding 20% or more. 

Comparing cannabis potency over time raises awareness of various factors affecting its measurement. Parts of the plant contain varying THC content: roots less than 0.03 %, stalks 0.1-0.3 %, leaves 1-2%, and flower 10-12% for example. Sinsemilla is cannabis flower from seedless female plants specifically tended to boost the trichome-rich flowering head increasing the THC percentage. Increased potency is facilitated by advancements in cultivation techniques, such as the use of artificial lighting, nutrient optimization, and the selection of high-THC genetics. Today in 2023, live resin and other cannabis concentrates have been documented to contain as much as 95% THC in a single product.  

While THC percentages have generally increased, there is still a wide range of cannabis strains available. THC levels can vary significantly depending on the specific strain, cultivation methods, and environmental factors. Additionally, the emergence of CBD-rich strains and the focus on other cannabinoids and terpenes has led to a diversification of cannabis profiles beyond just THC potency. 


THC percentage in cannabis has indeed changed significantly over the last 50 years. Due to advancements in cultivation techniques and selective breeding for higher potency strains, the average THC percentage in cannabis has increased. By the early 2000s, it became more common to find cannabis strains with THC levels ranging from 10% to 20%. In some cases, certain strains have even tested above 30% THC. Even though THC levels have increased, cannabis strains with lower THC and higher cannabidiol (CBD) percentages have also gained popularity in recent years due to the growing interest in therapeutic benefits and medical applications. 

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Written by Dana Neverdousky, MT(ASCP) and Veronica Martinez June 2023