A cannabis COA (certificate of analysis) is the lab report behind the label. When a batch of flower, vapes, edibles or concentrates is sampled, an independent testing laboratory measures what is in it and what is not, and the numbers on your package come from that report. Learning to read one takes about five minutes, and once you can, you will never look at a THC percentage the same way again.
This guide walks through a cannabis COA one section at a time, in plain English, the same way we explain it to neighbors at the counter on Court Street. No chemistry degree required. Adults 21 and over only.
What a cannabis COA is, and how it connects to your label
Every legal Illinois product carries a label with required information set out in Section 55-21 of the Cannabis Regulation and Tax Act. If the batch was sampled, that label must name the independent testing laboratory, show the date of final testing and packaging, list the minimum and maximum percentages of THC, THCA, CBD and CBDA, and carry a pass/fail rating based on the lab’s microbiological, mycotoxin, and pesticide and solvent residue analyses.
The label is the summary. The COA is the full report those summary lines come from. If you want a refresher on the label itself first, our guide on how to read an Illinois cannabis label covers all nine required elements.
Where do you find the COA? Some brands publish batch reports on their websites or link them from the package, and others do not make them public. The simplest move is to ask a budtender. If a report for that batch is available, we will help you pull it up.
How to read a cannabis COA in 7 steps
1. Match the batch before you read anything else
A COA belongs to one batch. Find the batch or lot identifier on the report and compare it to the serial number and batch details on your package. If they do not match, you are reading the report for somebody else’s jar, and none of the numbers apply to yours.
2. Check the lab name and the dates
Near the top you will see the testing lab’s name, the sample ID, and the dates the sample was received and the report was issued. The lab name should match the one on your label. Independent is the key word here: the grower does not grade its own homework.
3. Read the cannabinoid panel, and learn the one formula that matters
This is the section most people care about, and the one most people misread. Raw flower contains very little THC. It mostly contains THCA, the acid form, which converts to THC when heated. That is why a cannabis COA usually reports several lines:
- Delta-9 THC: THC already in its active form.
- THCA: the acid form, usually the biggest number on flower.
- Total THC: the combined figure most labels and menus lead with.
Total THC is calculated, not measured directly. The standard formula is Total THC = Delta-9 THC + (THCA × 0.877). The 0.877 accounts for the weight THCA loses when it converts. So a report showing 25.0% THCA and 0.8% delta-9 THC works out to roughly 0.8 + 21.9 = 22.7% total THC, not 25.8%. CBD and CBDA work the same way.
That formula is why two jars with similar “THC” claims can look different on paper. If you shop flower, total THC is the apples-to-apples number.
4. Watch the units
Results show up as a percentage, as milligrams per gram (mg/g), or for edibles as milligrams per serving or per package. The conversion is simple: 1% = 10 mg/g. So 22.7% total THC is 227 mg per gram. On an edible, look for the per-serving and per-package totals rather than a percentage.
Also look for “ND” (not detected) and “LOQ” (limit of quantitation). ND means the lab did not find that compound at a level its equipment can detect. A result below the LOQ means it may be present but in an amount too small to measure precisely.
5. Look at the terpene panel, if there is one
Not every cannabis COA includes terpenes, but many do. Terpenes are the aromatic compounds behind a strain’s smell and flavor, things like myrcene, limonene and caryophyllene. They are usually reported as a percentage or mg/g, with a total at the bottom. If aroma and flavor drive your choices, this panel is more useful than chasing the highest THC number. Our cannabis terpenes explained guide breaks down the common ones.
6. Read the contaminant screens
This is the part that leads to the pass/fail line on your label. Illinois labels report the pass/fail outcome for microbiological contaminants, mycotoxins, and pesticide and solvent residue. On the full report, each of those appears as its own panel, often with every compound listed next to the lab’s result and the allowed limit. Some reports also show extra panels such as heavy metals, moisture content or water activity.
Residual solvents matter most on extracts. If you are comparing concentrates or vapes, the solvent panel and the label’s extraction-method disclosure tell you how the oil was made. Our live resin vs live rosin post explains why solventless products show a different picture than hydrocarbon extracts.
7. Find the summary, then sanity-check it against the label
Most reports end with a one-line summary: pass or fail for each panel. Compare that to your label. Then compare potency. Illinois allows a tolerance band: under Section 55-21, the labeled minimum percentage for THC, THCA, CBD and CBDA may not be below 85% or above 115% of the labeled amount. A small gap between the COA and the label is normal. Treat any potency figure as a range, not a promise.
Three cannabis COA mistakes we see all the time
- Adding THCA and THC together. Use the 0.877 formula, or just read the Total THC line.
- Shopping on THC alone. Terpenes, freshness and format shape the experience as much as a single percentage does.
- Reading the wrong batch. A brand’s sample report from last spring tells you nothing about the jar in your hand. Always match the batch.
Reading a cannabis COA with us in Pekin
You do not have to do this alone. Browse what is in stock on our online menu, check this week’s deals, and bring your questions to the counter. Members of Pekin’s Local Rewards earn 8 points for every $1 before tax, and every 1,000 points is $5 off. It is free to join. Veterans, seniors and birthdays: just ask at the counter.
Curious how Illinois built its testing and licensing rules in the first place? The attorneys at Cannabis Industry Lawyer cover how the state regulates dispensaries and growers. For current possession limits, see the state’s official cannabis FAQ.
Cannabis COA FAQ
What does COA stand for on cannabis?
COA stands for certificate of analysis. It is the lab report from an independent testing laboratory showing a batch’s cannabinoid results and, where sampled, its contaminant screening. The potency figures and pass/fail rating on an Illinois label are drawn from that testing.
Why is total THC lower than THCA plus THC?
Because THCA loses weight when it converts to THC. The standard formula is Total THC = Delta-9 THC + (THCA × 0.877). A report showing 25.0% THCA and 0.8% delta-9 THC works out to about 22.7% total THC.
Does the COA have to match my label exactly?
No. Illinois allows a tolerance: the labeled minimum percentage for THC, THCA, CBD and CBDA may not be below 85% or above 115% of the labeled amount. Small differences are normal, which is why potency is best treated as a range.
Where can I see the COA for a product?
Some brands publish batch reports on their websites or link them from the package; others do not. Ask a budtender at Pekin’s Local Dispensary & Supply and we will help you find what is available for that batch.
Come see us on Court Street
We are at 359 Court St in downtown Pekin, open daily 10:00 AM to 9:00 PM, at (309) 620-0778. Bring a valid government-issued ID showing you are 21 or older.
For adults 21+ only. Consume responsibly. Valid government-issued ID required.