Quick answer
- Hemp products today
- The federal definition counts delta-9 THC only, at no more than 0.3% by dry weight
- Hemp crops today
- USDA requires a pre-harvest test for total THC, THCA included
- From December 11, 2026
- THCA counts toward total THC in the hemp definition itself
- Finished products from December 11
- No more than 0.4 mg of total THC, THCA included, per container
What THCA is
THCA, tetrahydrocannabinolic acid, is the form THC takes in the raw cannabis plant. Heat turns it into delta-9 THC, which is why a product's THCA matters even when its delta-9 figure is low.
USDA's hemp rule gives the arithmetic. Under 7 CFR 990.1, total THC equals 0.877 times THCA plus THC. The 0.877 accounts for the weight THCA loses as it converts.
Products and crops were measured differently
The federal definition in 7 U.S.C. 1639o sets its limit on delta-9 THC: no more than 0.3 percent on a dry weight basis. THCA is not named in it.
Farms are held to total THC. 7 CFR 990.3 requires the test of a hemp crop to "consider the potential conversion of THCA in hemp into THC" and to report total THC, from a sample taken within 30 days before harvest.
That gap is what let flower and other products with high THCA and low delta-9 THC be sold as hemp. The DEA's Schedule I listing for tetrahydrocannabinols, 21 CFR 1308.11, excludes anything that falls within the hemp definition, so the definition decides.
What changes on December 11, 2026
Section 781 of Public Law 119-37 closes the gap. The plant and its parts must hold no more than 0.3 percent "total tetrahydrocannabinols concentration (including tetrahydrocannabinolic acid)" on a dry weight basis.
A finished hemp-derived cannabinoid product may hold no more than 0.4 mg per container of total THC, THCA included, combined with any other cannabinoids that have similar effects as the Secretary of Health and Human Services determines. Flower whose THCA brings its total THC above 0.3 percent no longer meets the definition at all.
Section 781 takes effect November 12, 2026, but Public Law 119-103 holds back everything except the rule on cannabinoids the plant cannot produce naturally until December 11, 2026. The total THC rule is one of the parts that starts on December 11. The federal page has the full timeline.
State rules
States can be stricter than the federal definition, and several have written THCA into their own law. Read the state guides for Texas, Florida, Georgia, North Carolina and Tennessee.
Products with no THC and no THCA are untouched by the federal change: broad spectrum and isolate CBD, functional mushrooms and THC-free topicals.
Common questions
Is THCA legal under federal law?
Until December 11, 2026, the federal hemp definition in 7 U.S.C. 1639o tests products for delta-9 THC only, so it does not name THCA. From December 11, 2026, Section 781 of Public Law 119-37 counts total THC including THCA, and a finished product may hold no more than 0.4 mg of total THC per container.
How is total THC worked out?
USDA's hemp rule, 7 CFR 990.1, gives the formula: total THC equals 0.877 times THCA plus THC. The factor accounts for the weight THCA loses when heat turns it into THC.
Do state rules on THCA differ?
Some do. Tennessee, for example, has its own rules for hemp-derived cannabinoid products. See the state guides for the states we cover.
Sources
- 7 U.S.C. 1639o, definitions (the 2018 hemp definition), U.S. Code, Office of the Law Revision Counsel
- 7 CFR 990.1 and 990.3, definitions and sampling and testing, eCFR, National Archives
- Public Law 119-37, Division B, Title VII, Section 781, GovInfo, U.S. Government Publishing Office
- Public Law 119-103 (H.R. 6500), Section 2019, GovInfo, U.S. Government Publishing Office
- 21 CFR 1308.11, Schedule I (tetrahydrocannabinols), eCFR, National Archives
Each source was last read on November 5, 2026. Laws and rules change; check the source for the current text.