How to Read a Cannabis Lab Test (COA): A Plain-English Guide

Updated October 2026

Short answer: a cannabis COA (certificate of analysis) is a lab report for one specific batch. To read it, match the batch number to your package, confirm the lab is licensed and ISO/IEC 17025 accredited, find total THC (THC + THCA x 0.877), skim the terpenes, then make sure every safety test (pesticides, heavy metals, microbials, mycotoxins, solvents, water activity) says Pass.

That little QR code on your jar is the most underrated thing in the dispensary. Most people never scan it. The ones who do usually stare at a PDF full of acronyms, see a big THC number, and close it.

That's a shame, because a COA tells you more about your flower than any budtender pitch or strain name. We're a grinder company, so we care about what happens after the jar opens, and it all starts with what's actually in the jar. Here's how to read one in about two minutes, no chemistry degree required. (Adults 21+, buying from licensed shops where it's legal. Rules vary by state, so check yours.)

What a COA is (and isn't)

A certificate of analysis is a report from a testing lab showing what was found in a sample from one production batch. In licensed state markets, flower usually has to pass testing before it can be sold. California, for example, requires labs to test each batch for cannabinoids, foreign material, heavy metals, microbial impurities, mycotoxins, moisture content and water activity, residual pesticides, residual solvents and, when the label makes terpene claims, terpenoids, according to California's testing regulations.

What a COA isn't: a review, a guarantee about how a strain will feel, or proof about a different batch. It describes one sample from one batch on one date. That's it.

Step 1: find it and make sure it's real

• Scan the QR code on the package, or look up the batch on the brand's site. Many brands link the COA directly.
• Match the batch or lot number on the COA to the one on your package. If they don't match, the COA isn't for your product.
• Check the dates. Look for the sample collection date and the report date. A report from long before the package date is a yellow flag.
• Check the lab. The COA should name the lab, its state license number and its accreditation. California's Department of Cannabis Control states that licensed cannabis labs must maintain ISO/IEC 17025 accreditation, the international standard for testing-lab competence. Other states have similar rules. You can usually look up a lab's license on your state regulator's website.
• Open it from the lab if you can. A COA hosted on the lab's own portal is harder to tamper with than a PDF someone emailed around.

Step 2: read the potency section (THCA vs THC)

This is where most people get confused, so let's slow down.

Raw cannabis flower contains very little THC. It's mostly THCA, the acid form. When you heat it (lighting a joint, a bowl, a vape), THCA loses part of its molecule and converts to THC. That conversion is called decarboxylation.

Because THCA is heavier than THC, labs don't just add the two together. They use a conversion factor:

Total THC = THC + (THCA x 0.877)

The 0.877 accounts for the weight lost when THCA becomes THC, as the University of Georgia Extension explains. Here's what that looks like on a real-world style report:

So that "25% THCA" jar is really about 22.4% total THC. Not a scam, just math. Also note:

• % vs mg/g. 1% equals 10 mg per gram. A 22.4% flower has about 224 mg of total THC per gram.
• ND means "not detected." <LOQ means it was below the lab's limit of quantitation, the smallest amount it can measure reliably.
• Dry weight vs as-received. Some reports adjust for moisture. Wetter flower can read a little lower on an as-received basis.
• Minor cannabinoids like CBG, CBN and CBC may be listed. They're interesting, but potency numbers don't tell you how a particular strain will feel for you.

Why total THC matters more than ever (December 11, 2026)

This formula just became a big deal for hemp. For years, federal hemp rules only counted delta-9 THC, which is how high-THCA "hemp flower" ended up in gas stations. A November 2025 federal law redefined hemp to count total THC, including THCA, at no more than 0.3% on a dry-weight basis, and capped finished hemp products at 0.4 mg total THC per container. After a delay Congress passed in September 2026, most of that takes effect December 11, 2026, according to Foley Hoag.

Run the math: hemp flower with 18% THCA has about 15.8% total THC. That's more than 50 times the new limit. If you've been buying THCA flower, or you sell it, the potency section of the COA is now the whole ballgame. Our 2026 rescheduling and hemp explainer has the full timeline.

Step 3: read the terpene section

Terpenes are the aromatic compounds behind the smell and flavor of your flower: myrcene, limonene, beta-caryophyllene, pinene, linalool and friends. On a COA you'll usually see each terpene listed as a % or mg/g, plus a total.

• Look at the top two or three. They tell you more about the aroma than the strain name does. Two jars both called "OG" can have very different terpene profiles.
• Higher total terpenes usually means a more aromatic, flavorful flower, and it's a decent sign the batch was dried and cured with care.
• Not every COA has one. In California, terpene testing is only required when the label makes terpene claims, so a missing panel isn't automatically a bad sign.

Terpenes are volatile, which means they evaporate. Heat, light, air and rough handling all chip away at them after testing. More on that below. Our terpene guide goes deep on the common ones.

Step 4: check the safety panels

This is the part people skip, and it's the part that matters most. Every line should read Pass (or ND, or below the action limit).

A quick word on extracts and residual solvents

If you're reading a COA for a concentrate or vape, the solvent panel deserves a closer look. Hydrocarbon extraction (butane, propane) and ethanol extraction both rely on solvents that get purged afterward, and the test confirms they were. Supercritical CO2 extraction uses carbon dioxide under pressure instead. Solventless products like rosin use only heat and pressure, so there's nothing to purge, though they still get tested for everything else. Whatever the method, the COA is how you know the purge was done right.

Step 5: moisture and water activity (the freshness clue)

Water activity (aw) measures free water available for mold and microbes to use, on a scale from 0 to 1. It's different from moisture content, which is just the percentage of weight that's water. In California, dried flower and pre-rolls pass only if water activity doesn't exceed 0.65.

How to use it: very low numbers can mean over-dried, crumbly flower that burns hot and fast. Numbers right up near the limit suggest flower that was packaged on the wetter side. Somewhere comfortably in the middle usually means a proper dry and cure. If you grow your own, our home grow guide covers drying and curing.

Red flags: lab shopping and inflated THC

Here's the uncomfortable truth about COAs: the number on the label isn't always the number in the jar.

A 2023 peer-reviewed study in PLOS ONE retested 23 flower samples from 10 Colorado dispensaries. About 70% tested more than 15% below the THC on the label, and on average actual potency was 23.1% lower than the lowest labeled value. The authors pointed to "lab shopping," where growers and brands seek out labs that tend to report higher numbers, and noted a suspicious cluster of results just above 20% THC in some markets. Small study, but it matches what a lot of people in the industry say quietly.

Watch for these:

• Batch number doesn't match your package.
• Potency only. A COA with a big THC number and no safety panels is a sales sheet, not a full test.
• No lab license or accreditation listed, or a lab you can't find on your state regulator's site.
• A brand-made PDF with no way to verify it on the lab's portal.
• Suspiciously high THC across every product a brand sells, especially numbers stacked just above common marketing thresholds.
• Hemp products with no total THC line, only delta-9. After December 11, 2026, that's the number that counts federally.
• Very old test dates. Terpenes fade over time, so an old test may not reflect what's in the jar today.

After the COA: don't waste good flower at the grinder

You did the homework. You found a fresh, well-cured batch with a clean safety panel and a terpene profile you like. Now don't blow it in the last step.

Most of what you just paid for lives in the trichomes, the tiny resin glands on the outside of the flower. Dull grinder teeth and endless spinning mash flower into dust, smear resin on the teeth and knock trichomes loose before they ever reach your bowl. Here's how to keep more of it:

1. Grind right before you use it. Ground flower has more surface area, so it loses aroma faster. Keep the rest whole in an airtight jar, away from heat and light.
2. Use sharp teeth that cut, not pegs that crush. A few short twists back and forth, then a tap. The nerdy reasons are in the science of grind size.
3. Catch what falls. In a 4 piece grinder, loose trichomes sift through the screen into the bottom chamber as kief, so they end up in your next bowl instead of on the table.
4. Match the screen to your flower. Our Upgrade Kit includes 180, 300 and 400 micron screens if you want finer or coarser kief collection.

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FAQ

What does COA mean on cannabis?

COA stands for certificate of analysis. It's a lab report showing the cannabinoid content, terpenes and safety test results for one batch of product.

How do you calculate total THC from THCA?

Multiply THCA by 0.877 and add any delta-9 THC. For example, 20% THCA plus 0.4% THC equals about 17.9% total THC.

How do I know if a cannabis COA is legit?

Match the batch number to your package, confirm the lab is state-licensed and ISO/IEC 17025 accredited, and pull the report from the lab's own portal when possible. Make sure safety panels are included, not just potency.

Is higher THC always better?

No. Potency numbers can be inflated, and THC alone doesn't describe the aroma, flavor or overall experience. Freshness, cure and terpene content matter too.

What is a good water activity for cannabis flower?

In California, flower must test at or below 0.65 water activity to pass. Very low readings can mean over-dried flower, while readings near the limit mean it was packaged on the wetter side.

Read the label, trust the lab (after you verify it), and then treat that flower right.

Keep reading

• What are trichomes, and why your grinder should protect them
• Understanding cannabis terpenes
• Smoke shop trends for 2026 and 2027