How to read a COA: the total THC line and nine other checks

The short answer. Find the line labeled Total THC. It should equal delta-9 THC plus 0.877 times THCA, reported on a dry-weight basis. Then confirm the report belongs to the product: the lot number matches, the lab is accredited, and the lab’s own site shows the same report. From Dec. 11, 2026, that total THC line, not delta-9 alone, is what federal law reads.

A certificate of analysis, or COA, is a lab’s report on one sample from one lot. Read it like a document with a chain of custody, not a sales sheet.

The ten checks, in order

#	Check	Where on the report	What a sound report shows	Red flag
1	Lot or batch number	Header, sample information	Same number as the package label	No lot number, or one that matches nothing you were sold
2	Lab identity	Header and footer	Lab name, address, license or registration	A logo with no address or license
3	Accreditation	Footer or first page	ISO/IEC 17025 accreditation body and certificate number	No accreditation, or an expired certificate
4	Dates	Header	Sample collected, received and reported, within a sensible span	A report dated long before the product was harvested
5	Who sampled	Sample information	Sampled by the lab or a third-party sampler	“Client submitted” with no further detail
6	Method	Potency page	HPLC or UHPLC for separate THCA and delta-9 lines	No method listed
7	Basis	Potency page	“Dry weight” stated, with moisture reported	Basis not stated
8	Total THC math	Potency summary	Delta-9 + 0.877 × THCA, within rounding	A total that does not match the lines above it
9	Safety panels	Later pages	Pesticides, heavy metals, microbials, mycotoxins, with pass or fail	Potency only, on a product sold to smoke
10	Verification	Footer, QR code	Report retrievable on the lab’s own domain	QR code that lands on the seller’s site

Reading the cannabinoid table

A potency table usually has four kinds of columns:

• Percent (w/w). Grams of the compound per 100 grams of sample.
• mg/g. The same number times 10. A line reading 24.6 percent also reads 246 mg/g.
• LOD and LOQ. The limit of detection is the smallest amount the method can see; the limit of quantitation is the smallest amount it can measure reliably. Each lab sets its own.
• Result codes. ND means not detected (below LOD). <LOQ means detected but too small to put a number on.

Checking the total THC line yourself

Take the THCA and delta-9 lines and do the arithmetic. A worked example:

Line	Value
THCA	24.6%
Delta-9 THC	0.21%
0.877 × 24.6	21.57%
Total THC	21.78%

If the report prints a total that differs by more than rounding, ask why. Some labs print a “Total THC” that adds delta-9 and THCA without the 0.877 factor, which overstates the figure; others print only delta-9 under a “THC” heading. The 0.877 factor is the conversion the USDA itself prescribes: delta-9 THC plus 87.7 percent of THCA (7 CFR 990.1).

A useful benchmark: with no delta-9 at all, flower can hold only about 0.34 percent THCA and stay at or under 0.3 percent total THC. Anything sold as THCA flower is far above that line by design.

Dry weight versus “as received”

Fresh plant material holds water, and water dilutes every percentage. Federal law sets hemp limits “on a dry weight basis.” A lab that reports “as received” has not made that correction.

To convert, divide by the dry fraction. At 10 percent moisture, a THCA result of 22.0 percent as received is 22.0 ÷ 0.90 = 24.4 percent on a dry-weight basis. Converting raises the number, which matters most when a sample sits near a legal limit.

Measurement uncertainty

Every measurement has a margin. The USDA’s grower rule builds it in: a result passes if its range, after applying the lab’s uncertainty, reaches 0.3 percent or below. The rule’s own example is a result of 0.35 percent with an uncertainty of ±0.06, a range of 0.29 to 0.41 percent, which counts as acceptable (7 CFR 990.1). That rule governs crops in the field. States set their own approach to finished products, so check whether a report states its uncertainty.

Liquid versus gas chromatography

Liquid chromatography leaves THCA intact and reports it on its own line. Gas chromatography heats the sample, converting THCA into THC inside the instrument, and reports something close to total THC as a single number. The USDA accepts either for growers (7 CFR 990.3). A flower COA that shows separate THCA and delta-9 lines tells you more, because you can check the math.

The safety pages

Potency is one page; the rest tell you whether the flower is clean. Look for these panels and a pass or fail against a stated action limit:

Panel	What it covers
Pesticides	Residues of agricultural chemicals, usually dozens of compounds
Heavy metals	Arsenic, cadmium, lead and mercury
Microbials	Salmonella, shiga-toxin E. coli, and for inhaled products often Aspergillus species
Mycotoxins	Aflatoxins and ochratoxin A, produced by molds
Moisture and water activity	Indicators of how likely mold is to grow
Foreign matter	Visible contaminants such as hair, insects or debris

Action limits come from a state’s rules, so a report should say which state’s limits it applied. A pass in one state is not automatically a pass in another.

What the total THC line means after Dec. 11

Until Dec. 10, 2026, federal hemp status turns on the delta-9 line. From Dec. 11, under Section 781 of Public Law 119-37 as delayed by H.R. 6500, it turns on total THC at 0.3 percent, plus a 0.4 mg total-THC cap per container for final products. A report can be accurate and complete and still show, in its own numbers, that the flower is not hemp. Our Hemp Ban Tracker carries the dates; THCA vs. THC explains the chemistry behind the factor.

Sources

• 7 CFR 990.1, USDA definitions, including decarboxylated value and measurement of uncertainty
• 7 CFR 990.3, USDA sampling and testing requirements
• 7 U.S.C. 1639o, current hemp definition
• CRS In Focus IF13136, the new definition, Aug. 17, 2026

Reviewed Oct. 3, 2026. This guide explains how to read lab reports; it is not legal advice.

Questions readers asked

Where is the total THC on a COA?

Usually in the cannabinoid summary at the top of the potency page, labeled Total THC or Total Δ9-THC. It should equal delta-9 THC plus 0.877 times THCA, on a dry-weight basis.

What does ND or <LOQ mean on a COA?

ND means not detected: below the lab's limit of detection. <LOQ means the lab saw the compound but below the lowest level it can measure reliably, its limit of quantitation.

How do I know a COA is real?

Match the lot or batch number to the package, check the lab's accreditation to ISO/IEC 17025 and its certificate number, and look the report up on the lab's own website or portal rather than relying on a PDF or QR code alone.

What total THC is legal after Dec. 11, 2026?

Under federal law as of Oct. 3, 2026, hemp must be at or below 0.3 percent total THC on a dry-weight basis from Dec. 11, 2026, and final products face a 0.4 mg total THC cap per container.

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