Free tool. On November 12, 2026, federal law (Public Law 119-37, Section 781) redefines hemp from a delta-9-only standard to a total THC standard: total THC = delta-9 THC + (0.877 × THCA), capped at 0.3% by dry weight. Enter values from any Certificate of Analysis to see how a product measures under both the current and future rules. Free to use and free to embed — see below.
General information, not legal advice. State law may be stricter than federal law and enforcement varies. Verify against current statute and your Certificate of Analysis. Adults 21+ only.
Why the Formula Uses 0.877
THCA converts to delta-9 THC when heated (decarboxylation). Because THCA is a heavier molecule, the conversion loses a carboxyl group — a factor of roughly 0.877. The total-THC standard counts that potential conversion up front rather than measuring only what is present in the raw material. A flower testing 20% THCA computes to about 17.5% total THC, far above the 0.3% threshold, even where its delta-9 reading is compliant under today's rule.
Embed This Calculator on Your Site
Free to use on any site. Copy the snippet below:
Prefer a simple text link? <a href="https://docs-hemp.com/total-thc-calculator/">Total THC Calculator (Nov 12, 2026 hemp rule)</a>
Related Resources
- What changes for THCA on November 12, 2026
- How to read a Certificate of Analysis
- THCA legality by state
- What is a good THCA percentage?
Last reviewed: August 4, 2026. Maintained by Doc's Hemp.
See also: THCA Legal Status Checker — check your state.