How to Read a THCA Flower COA: Total THC vs. Delta-9 THC

One number on that lab report decides whether your flower is legal. Most people never look at it.

Every reputable THCA flower listing links a COA — a Certificate of Analysis from a third-party lab. Most buyers open it, find the biggest percentage on the page, decide the flower is strong, and close the tab.

That big number is usually THCA. It is not the number that determines legality, and it is not the number regulators use. The number that matters is total THC, and on a lot of COAs you have to calculate it yourself.

Here's how to read the whole document like someone who grows the plant.

The formula, straight from the regulation

This isn't industry folklore. It's federal code. Under 7 CFR 990.1, total THC is "the value determined after the process of decarboxylation, or the application of a conversion factor if the testing methodology does not include decarboxylation, that expresses the potential total delta-9 tetrahydrocannabinol content derived from the sum of the THC and THCA content and reported on a dry weight basis."

When a lab uses liquid chromatography — which most do, because it doesn't destroy the acid forms — the regulation prescribes the arithmetic exactly:

Total THC = (0.877 × THCA) + delta-9 THC

The 0.877 isn't arbitrary. THCA is THC wearing an extra carboxyl group. Apply heat — a lighter, a vaporizer, an oven — and that group leaves as carbon dioxide. What's left weighs about 87.7% of what you started with. So 0.877 is simply the mass that survives the reaction.

Run it on a real-looking flower

Say a COA on a jar of flower reports 22.0% THCA and 0.15% delta-9 THC.

(0.877 × 22.0) + 0.15 = 19.44% total THC

Two facts sit in that one line, and they don't contradict each other:

• That flower is federally compliant hemp today. As of August 2026, the operative federal definition — from the 2018 Farm Bill — is not more than 0.3% delta-9 THC on a dry weight basis. At 0.15%, it clears with room to spare.
• It is nowhere close to compliant under a total-THC standard. 19.44% against a 0.3% ceiling isn't a near miss. It's two orders of magnitude.

That gap is the entire THCA flower category. It's also exactly what Congress voted to close — see our breakdown of the Senate's vote to delay the federal hemp THC ban for where that stands right now.

Here's the subtler version, the one that actually shows up in a field test. A grower's sample comes back at 0.28% delta-9 and 1.2% THCA:

(0.877 × 1.2) + 0.28 = 1.33% total THC

Passes on delta-9. Fails a total-THC standard by more than four times. This is why "we test in the field and we've never had a hot crop" means very different things depending on which rule the tester was applying.

The rest of the page, top to bottom

The lab. Look for a named third-party laboratory with ISO 17025 accreditation. A COA produced by the same company selling the flower is a self-report, not a test. USDA's lab testing guidelines also require labs doing compliance testing to be registered with the DEA.

Sample ID and batch number. These should match the batch code on the jar or bag you received. A COA that doesn't tie to your specific lot is a marketing PDF. This is the single most common place a reseller's paperwork falls apart — one good COA gets attached to a year of different material.

Date. Cannabinoids degrade. THCA slowly converts, terpenes evaporate. A COA from eighteen months ago describes flower that no longer exists in that condition.

"Dry weight basis." The regulation specifies it, and it matters. Moisture content moves percentages. A wet sample reads artificially low.

Measurement of uncertainty. Serious labs report it, and federal code builds it in: an "acceptable hemp THC level" occurs when applying the measurement of uncertainty to the reported concentration "produces a distribution or range that includes 0.3 percent or less." A result of 0.31% ± 0.05% is still compliant hemp. Missing MU on a compliance COA is a sign the lab is cutting corners.

ND vs. <LOQ. "ND" means not detected. "<LOQ" means present but below the level the instrument can reliably quantify. They are not the same claim, and a lab that uses them interchangeably is being sloppy with the only thing you're paying it for.

The panels past cannabinoids. Potency is one test. A complete COA package also covers pesticides, heavy metals, residual solvents (for concentrates), and microbials. Flower is an agricultural product grown in soil and combusted in your lungs — heavy metals matter more here than the potency line does. If a vendor only ever shows you the cannabinoid page, ask why.

Red flags, in order of how often we see them

1. No batch match. The COA's sample ID doesn't correspond to anything on your package.
2. A flattened image instead of a lab-issued PDF. Real labs publish reports with verification links or QR codes back to their own portal. A JPEG of a COA can be edited by anyone with a phone.
3. Total THC omitted entirely. When a seller shows THCA and hides the total, that's a choice.
4. Potency only, no safety panels. Especially on imported or brokered material.
5. Percentages that don't add up. If the listed total THC doesn't reconcile with (0.877 × THCA) + delta-9, something was typed by hand.
6. An unnamed or unaccredited lab. Or no lab name at all.

Why we care about this more than most sellers do

Diesel Hemp grows in Loveland, Colorado. We put the seed in the ground, we cut it, we cure it, and the batch on the COA is the batch in the jar — because there's only one place it could have come from.

That's not a marketing line, it's a paperwork advantage. A company buying bulk flower from three brokers in two states has a genuinely hard time keeping COAs matched to lots, because the material and the documents travel separately. We don't have that problem, and as the compliance standard tightens toward total THC, the operators who can point at a field and a batch record are the ones who'll still be shipping.

Once you can read the report, the flower gets more interesting too. Cannabinoid percentages are the least informative thing on the page — the terpene profile tells you far more about what an experience will actually be like. If your COA includes terpenes, that's where to spend your attention: a limonene-dominant Sour Diesel and a terpineol-heavy Chemdawg can post nearly identical THCA numbers and land completely differently.

Every batch of our THCA flower and pre-rolls ships with its own lab report. Pull one up and run the formula yourself — it takes ten seconds, and once you've done it once you'll never read a listing the same way again.

Frequently Asked Questions

What is total THC on a COA?

Total THC is the potential delta-9 THC content of a sample after THCA converts, expressed on a dry weight basis. Under 7 CFR 990.1, when a lab uses a method that doesn't decarboxylate the sample, it's calculated as (0.877 × THCA) + delta-9 THC.

Why is the conversion factor 0.877?

THCA is THC with an additional carboxyl group. When heat removes that group, it leaves as carbon dioxide, and the remaining THC weighs roughly 87.7% of the original THCA. The factor is the ratio of the two molecules' masses, not an estimate of how much converts in practice.

Is THCA flower legal if total THC is over 0.3%?

As of August 2026, yes at the federal level — the operative definition from the 2018 Farm Bill sets the limit at not more than 0.3% delta-9 THC on a dry weight basis, not total THC. That definition is scheduled to change to a total-THC standard when the provisions of the November 2025 appropriations package take effect. State law varies independently, and several states restrict or prohibit these products regardless of federal status.

What does ND mean on a lab report?

ND means "not detected" — the compound was below the instrument's limit of detection. It's distinct from "<LOQ," which means the compound was detected but below the limit of quantitation, so the lab can confirm its presence but not its amount reliably.

How current does a COA need to be?

There's no single federal expiration rule, but cannabinoids and terpenes both degrade with time, light, and heat. Match the COA to your specific batch first; then treat a report older than about a year as describing a different product than what's in the jar.

What is measurement of uncertainty on a COA?

It's the range of values that could reasonably be attributed to the measurement, given the limits of the instrument and method. Federal code incorporates it directly: hemp is at an acceptable THC level when the reported concentration plus or minus its uncertainty produces a range that includes 0.3 percent or less.