How to read a Certificate of Analysis

A COA isn't marketing. It's the receipt. Here's every section, the math behind total THC, and the red flags that should kill a sale.

The header is the part most people skip

Every legitimate Certificate of Analysis starts with the boring stuff: the testing lab's name and address, the lab's accreditation (the credential to look for is ISO/IEC 17025), the producer's name, the batch ID, the sample ID, the strain or product name, and the test date. If any of those fields are missing or vague, the document is decorative — not evidence.

Match the batch ID on the COA to the batch ID on the package. They should be identical. A COA from a different harvest is not your COA.

The cannabinoid panel

Expect to see THCa, Δ9-THC, Δ8-THC, CBD, CBDa, CBG, CBN, and total cannabinoids — all reported as percentages by weight. For Farm Bill compliance the only number that has to be at or below 0.3% is Δ9-THC. THCa can be high (15–30%+ on quality flower) and the product is still hemp.

The total THC formula

Active total THC = (THCa × 0.877) + Δ9-THC. The 0.877 multiplier accounts for the mass lost when the carboxyl group leaves during decarboxylation. So a flower listed at 25% THCa and 0.2% Δ9-THC has roughly 22.1% active THC potential after heat. That's the number to compare across products, not the headline THCa percentage.

If a brand prints a giant THCa number on the bag and you can't find a COA to back it, the number is a guess.

Terpene panel

Not every COA includes terpenes. The ones that do tell you the most about how a strain will feel. Caryophyllene reads peppery and relaxing. Limonene is bright, citrus, alert. Myrcene is the sedating, couch-pulling end. Pinene is sharp and clear. Linalool is floral and sleepy. A 2017 review in the British Journal of Pharmacology summarized the case for terpenes contributing meaningfully to the entourage effect — the practical version is that terpene profile predicts feel better than total THC.

Safety panels are pass/fail

Four sections you check fast: pesticides, residual solvents, heavy metals, microbials and mycotoxins. Each line should read PASS, ND (non-detect), or a value below the action limit. A single 'NT' (not tested) on a flower or concentrate safety panel is a hard pass.

What 'clean' actually means

Residual solvents apply to extracted concentrates — solventless rosin should show ND across the board because no solvent was used. Pesticides and heavy metals apply to anything grown in soil. Microbial limits cover yeast, mold, and Aspergillus species; flower above the threshold is unsafe to smoke regardless of how it looks.

Red flags

No accreditation listed on the lab. PDF that's actually just a screenshot. No batch ID. Test date older than the harvest date (yes, this happens). Cannabinoid percentages that don't add up to a plausible total. Safety panels missing entirely. Any one of these and the document isn't a COA, it's a graphic.