Answer first: a potency lab report tells you how much THC, THCA, CBD, and related compounds are in the batch you are holding, and for flower and concentrates the number that matters is total THC, not the THC line alone. To read one, find the certificate of analysis (COA), confirm the lab name, license number, batch ID, and test date, then check total THC and total CBD along with the units used (percent for flower and vape, milligrams for edibles). The top pick for shoppers who want verifiable numbers is any product whose COA is printed on the package or posted by the retailer, because that is the only version you can match to your exact batch. The criteria below separate a usable report from a decorative one: lab identity, batch traceability, test date, a full testing panel, and clear units.
Does Lab-Tested Cannabis Guarantee Safe? What a COA Proves and What It Misses
What the potency panel actually measures
Potency testing uses chromatography to separate and quantify cannabinoids. Most reports list:
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- THC: the already active form.
- THCA: the acid form found in raw flower, which becomes THC when heated.
- CBD and CBDA: the same split for cannabidiol.
- Total THC and total CBD: the combined value after conversion.
- Minor cannabinoids: CBG, CBC, CBN, and THCV, when the lab reports them.
How to calculate total THC
Total THC = THC + (THCA x 0.877). The 0.877 factor accounts for the mass lost when the acid group leaves during decarboxylation.
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Example: a flower sample listing 0.9% THC and 24% THCA works out to 0.9 + (24 x 0.877) = 0.9 + 21.05, or about 21.9% total THC. If a package markets the 24% figure as its THC content, it is quoting THCA and overstating what the flower delivers.
Percent labels versus milligram labels
Both formats are legal and both are useful, but they answer different questions.
Percentage labels (flower, vape cartridges, concentrates)
- Pros: easy to compare two strains or two jars side by side.
- Pros: independent of package size, so a 3.5 g jar and a 1 g jar stay comparable.
- Cons: says nothing about how much material you actually receive.
- Cons: concentrates can reach 80% or higher, which makes percentage a poor guide to dose.
Milligram labels (edibles, tinctures, capsules)
- Pros: shows exactly how much THC sits in each serving and in the whole package.
- Pros: makes dose control practical, which matters for anyone new to edibles.
- Cons: the per serving number and the per package number are easy to confuse.
- Cons: a package can hold ten servings, so the total is far larger than one dose.
Use-case recommendation: judge flower and vape by total THC percentage, and judge edibles by milligrams per serving with the package total written down.
The rest of the certificate: what else to scan
A potency column on its own is not a full report. A complete certificate of analysis carries:
- The testing lab name and license or accreditation number.
- A sample ID, batch or harvest lot number, and the date the sample was collected.
- The date results were reported, so you know how old the data is.
- The full panel: potency, terpenes, pesticides, microbials, heavy metals, residual solvents, mycotoxins, moisture, and water activity.
- Method notes, usually HPLC or GC.
Two abbreviations show up often. ND means not detected. A result written as less than the LOQ means the compound fell below the limit the instrument can reliably quantify, which is not the same as zero but is close enough for label purposes.
The method changes how you read the acid forms. GC uses heat at the inlet, which converts THCA into THC, so those reports usually show one combined THC value. HPLC keeps compounds separate, so you will see THC and THCA listed apart and you do the 0.877 math yourself.
Red flags on a potency report
- No lab name, no license number, or no accreditation listed.
- No batch or lot number that matches your package.
- No collection date, or a test date that predates the harvest.
- Potency numbers with no contaminant panels attached.
- Round numbers across the board, such as 25.0% THC, with no supporting detail.
- A QR code that leads to a generic page rather than a batch specific report.
Five step checklist before you buy
- Match the batch or lot number on the COA to the number on your package.
- Find total THC, not the THC line, and confirm the units.
- Check total CBD if you are buying for a specific reason.
- Scan the contaminant panels and the pass or fail column.
- Note the report date and lab name so you can compare future batches.
Why total THC is not the same as how high you get
Potency is one variable among several. Terpene content, flower moisture, how you consume it, and your own tolerance all shape the experience. A 30% total THC flower with a dry cure can feel flatter than a 22% flower with intact terpenes. Treat the COA as accuracy data about the product rather than a prediction of the effect, and use it to track batches of the same strain over time.