Total Delta-9 THC Math

In Texas today, one number decides whether a consumable hemp product is legal hemp: total delta-9 THC, on a dry weight basis, at 0.3% or less — read together with the lab's measurement of uncertainty. That is how the rule defines the 'acceptable hemp THC level' (25 TAC §300.101(1)), and it is the number the testing rule applies before a product can be sold (§300.301(b)(4)) and the number the department is required to check in random retail testing (§300.302(c)(3)).

Two things that number is not. It is not delta-9 THC alone — THCA counts toward it through a conversion factor. And it is not 'total THC' — that is a separate defined term in the same rule (all THC isomers plus THCA) which must also appear on the COA, but it is not today's Texas legality threshold. If you take one thing from this lesson: for Texas legality today, read the line labeled total delta-9 THC.

The Texas definition does the work for you. 25 TAC §300.101(45) defines total delta-9 THC as 'the sum of delta-9 THC and THCA, reported on a dry weight basis,' and when the lab's method keeps THCA intact (liquid chromatography), the rule prescribes the conversion in brackets: [Total delta-9 THC = (0.877 x THCA) + delta-9 THC].

Why 0.877? When hemp is heated — smoked, baked, or run through a gas chromatograph — THCA converts to delta-9 THC and loses mass in the process. The definition covers both lab routes: a heat-based technique like gas chromatography converts the THCA during testing, so the result already includes it; a liquid chromatograph keeps THCA intact, so the 0.877 conversion is applied instead. The federal hemp regulations use the same factor and call it what it is: 'a molecular mass conversion ratio that sums delta-9 THC and eighty-seven and seven tenths (87.7) percent of THC-acid' (7 CFR §990.1).

One more phrase that matters: dry weight basis. The percentage is measured against the sample with moisture removed. Every number in this lesson, and every THC percentage on a Texas COA, is a dry-weight figure — that comes from the definitions themselves.

Texas requires the COA to report three THC results for the sample: percentage of delta-9 THC, total delta-9 THC, and total THC per container (§300.301(d)(12)). They answer different questions.

Delta-9 THC is the raw delta-9 reading alone. Total delta-9 THC is delta-9 plus converted THCA — today's Texas legality number. Total THC is the broadest: the rule defines it as the sum of all THC isomers and THCA content, with its own bracketed conversion [Total THC = (0.877 x THCA) + THC] (§300.101(44)). Total THC must be on the COA, and it becomes very important on the federal side soon — but under the Texas rules in force today, the 0.3% threshold is written on total delta-9 THC, not total THC.

A COA that reports only delta-9 and leaves the totals blank is missing required fields — that is a defect in the document itself, before you ever reach the math.

You can redo every one of these on a phone calculator. All figures are dry-weight percentages; these are illustrations of the rule's formula, not lab data.

Example 1 — passes delta-9-only, fails total delta-9. A flower COA reports delta-9 THC 0.10% and THCA 0.50%. Old delta-9-only eyes see 0.10% and relax. The rule's math: total delta-9 THC = (0.877 x 0.50) + 0.10 = 0.4385 + 0.10 = 0.5385% — call it 0.54%. That is well over 0.3%. This product is not legal hemp under the Texas definition.

Example 2 — passes. A tincture COA reports delta-9 THC 0.12% and THCA 0.15%. Total delta-9 THC = (0.877 x 0.15) + 0.12 = 0.13155 + 0.12 = 0.25155% — about 0.25%. Under 0.3% before the uncertainty range is even considered.

Example 3 — the THCA trap in its purest form. A 'THCA flower' COA reports delta-9 THC 0.03% and THCA 0.90%. Total delta-9 THC = (0.877 x 0.90) + 0.03 = 0.7893 + 0.03 = 0.8193% — about 0.82%, nearly three times the threshold. Products marketed on a high THCA number with a tiny delta-9 number are exactly what the total delta-9 definition exists to catch.

The threshold is not applied to a bare number — it is applied to the number as reported with the lab's measurement of uncertainty (MU), the ± that describes how much the measured value could reasonably vary. The rule's own definition walks through the example: if reported total delta-9 THC is 0.35% dry weight and the MU is +/- 0.06%, the measured range runs from 0.29% to 0.41% — and 'because 0.3% is within the distribution or range, the sample is within the acceptable hemp THC level' (25 TAC §300.101(25)).

Run the same logic on a report of 0.38% with the same +/- 0.06%: the range is 0.32% to 0.44%, which does not include 0.3% — that sample is outside the acceptable level. The MU range is a defined statistical window reported by the accredited lab, not a grace margin you can invoke; if the range the lab reports does not reach 0.3%, the product fails. That is also why MU analysis parameters are themselves a required COA field (§300.301(c)(2), (d)(11)) — without them, the threshold in §300.101(1) literally cannot be applied to the document.

Texas today (in force now): legality is total delta-9 THC — delta-9 plus 0.877 x THCA — at 0.3% or less, dry weight, read with MU. Total THC is reported on the COA but is not the Texas threshold.

Federal, taking effect November 12, 2026: Section 781 of the FY2026 Appropriations Act (signed November 2025) redefines federal hemp from 0.3% delta-9 THC to 0.3% total THC — expressly including THCA — and caps finished products at 0.4 milligrams of combined total THC and cannabinoids with similar effects per container. That standard is broader than today's Texas number on both axes: it counts all THC isomers (not only delta-9 plus THCA), and the per-container cap reaches beyond THC to similar-effect cannabinoids. None of it is in force yet.

The practical read for a Texas retailer: the total delta-9 column decides today; the total THC column on the same COA previews the federal test that arrives November 12, 2026. A product can sit under the Texas line and over the coming federal one — that is a conversation to have with your suppliers and your attorney now, not on November 11.

Any of these should stop a product before it reaches a shelf: