THC, THCA, Total THC – What’s The Difference?


The hemp industry is still relatively young, and those working in this new sector must navigate recently-drafted regulations with unique and unfamiliar legal jargon. Federally, it’s a legal crop, but each state handles it differently and definitions of what is and is not legal or required for compliance may vary state to state.

In addition to the inconsistency of regulations, the plant itself is not well understood due to outdated laws that failed to distinguish hemp from its genetic cousin, marijuana. However, as hemp and CBD become more popular and accepted, information about the plant is more accessible than ever, but the language used to discuss the plant can still be a source of confusion.

This can lead to headaches as growers and processors try to figure out exactly how much THC is in their crop versus the amount they’re legally allowed to have. Read below for a deep dive into THC and the other must-know terms for ensuring compliance. 

THC – Tetrahydrocannabinol

THC is just one of hundreds of cannabinoids, which are naturally occurring compounds found in cannabis, of which hemp is a variety. When consumed, these cannabinoids interact with receptors in the human brain and nervous system, creating specific physiological effects. 

THC is the psychoactive cannabinoid found in cannabis that produces the “high” associated with marijuana. While this compound has been mostly bred out of hemp plants, trace amounts can still be found. When hemp was legalized by the 2018 Farm Bill, the bill stipulated that in order to be considered hemp, plants could not contain more than 0.3 percent of THC.

THCA – Tetrahydrocannabinolic Acid

Another cannabinoid, THCA can also be found in hemp. It’s important to be aware and understand THCA because it can convert to THC as the plant ages, dries, or gets exposed to extreme environmental conditions. It’s recommended that farmers monitor their crops’ THCA levels near harvest to be aware of potential for the final THC figure to climb. 

Total THC (sometimes called Max THC)

The 2018 Farm Bill mandated that both THC and THCA need to be taken into consideration when determining whether a plant falls under the 0.3 percent THC requirement. “Total THC” accounts for both THC and THCA, however, in this calculation, THC is added to 0.877 percent of the THCA present in the plant. The number 0.877 is used because it’s the percentage of THCA that remains after decarboxylation, the process where heat, time, or both convert THCA into THC. The end result would be the maximum amount of THC that could be found in the plant when it has dried. 

The equation to calculate a plant’s Total THC is THC + (THCA x 0.877)

Note: CBD and CBDA have this same relationship, and Total CBD can be determined via the formula CBD + (CBDA x 0.877)

Delta 9 

Delta 9, also called D9 or displayed as Δ9, is short for delta-9-tetrahydrocannabinol. This is actually the full chemical name for THC, which specifies the particular structure of the molecule itself. Delta-9-THC is currently not legal under the federal law, and plants with more than 0.3 percent THC on a dry weight basis are classified as marijuana, which is a controlled substance.

Delta 9 is the primary molecule responsible for most of the psychoactive effects of federally illegal varieties of cannabis. It is much stronger, and slightly structurally different, than its isomeric relative Delta-8-THC.

Delta 8 

Delta 8 is short for delta-8-tetrahydrocannabinol. Delta 8 is also psychoactive but at a much lower strength and occurs significantly less in cannabis or hemp. Whether this cannabinoid is legal is still a gray area under federal law, but it’s helpful to be aware of Delta-8-THC in case laws or regulations change.


It’s important to understand all these terms and their definitions because, while most regulations will only reference the 0.3% THC limit, all of these factors can affect the legality of your crop. 

Understanding Total THC and being able to calculate it will provide critical information about how much THC will occur in your harvested and dried crop, extracted oil, or infused product. This data is critical for quality control as well as for staying compliant at every stage of production.

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