THC percentage on a cannabis label is the weight of tetrahydrocannabinol divided by the total product weight, times 100. One gram of flower labeled 20% THC holds about 200 mg of THC by weight. The number comes from a lab test on a sample pulled from a batch, not from the package in your hand.
Cannabis Label Dosage for Edibles Explained
What the Number Measures
The percentage covers delta-9 THC, the compound that binds cannabinoid receptor 1 and produces the psychoactive effect. It does not cover the whole plant. Water, plant fiber, and other cannabinoids fill the rest of the mass.
cannabis label meaning of lot number
Total THC and THCA
Raw cannabis stores most of its THC as THCA, the acid form. THCA does not produce a high until heat removes a carboxyl group in a process called decarboxylation. Regulated states require labels to list THCA and delta-9 THC as separate figures, then a total. The standard calculation:
Total THC = delta-9 THC + (THCA x 0.877)
how to interpret cannabis lab test results
The 0.877 factor accounts for the mass lost when the carboxyl group leaves. Flower tested at 25% THCA and 1% delta-9 THC works out to about 22.9% total THC. A label that prints only the THCA figure overstates what you can absorb.
How Labs Produce the Number
Licensed labs use high-performance liquid chromatography to separate and measure cannabinoids. A technician grinds and mixes a sample, then runs it against known standards. Colorado and other states require potency testing before retail sale. The result applies to the batch, which can run to hundreds of plants and dozens of pounds. A single bud may test above or below the label figure.
Why Two Labs Report Different Numbers
- Sample location. THC concentrates in upper flower, near the top of the plant.
- Sample size and grind. A few grams stand in for a large batch.
- Method and calibration. Equipment, reference standards, and moisture correction vary by lab.
- Storage and age. THC degrades to CBN over months, faster with heat and light.
Published comparison studies find differences in reported potency for the same material across labs. Moisture content shifts the ratio as well. A dry sample reports a higher percentage than the same material with its water weight intact.
Common Ranges by Product Type
- Flower: 12% to 30% total THC in the legal US market. Most tested flower lands between 15% and 25%.
- Pre-rolls: 10% to 25%.
- Vape cartridges and concentrates: 60% to 90%.
- Tinctures: listed as mg per bottle or mg per milliliter.
- Edibles: 5 mg or 10 mg per serving in most states. California and Colorado cap a package at 100 mg.
Turning Percentage Into Dose
Multiply product weight by the percentage. Example: 0.5 g of 20% flower = 500 mg x 0.20 = 100 mg of THC in the material. Inhaled bioavailability estimates in published research run from about 10% to 35%, because combustion destroys part of the THC and sidestream smoke carries more away. Edibles lose little in the gut but convert THC to 11-hydroxy-THC in the liver, which changes onset time and duration.
What the Percentage Does Not Tell You
It says nothing about terpenes, flavonoids, or minor cannabinoids such as CBG, CBC, and CBN. Some labels carry those figures with their own percentages. High THC flower can hold fewer terpenes by weight, since every compound draws from the same mass budget. Research has not settled whether the full set of compounds changes the effect beyond THC alone.
Other Numbers on the Label
- THCA, delta-9 THC, and total THC.
- CBD and minor cannabinoid content.
- Terpenes in mg per gram or as a percentage.
- Batch or harvest date, since THC declines over time.
- Test date and the name of the lab.
- Net weight in grams or milligrams.
Practical Steps at the Counter
- Read total THC, not the largest number printed on the package.
- Compare mg per package for edibles, not percentage.
- Ask for the harvest date on flower.
- Start edibles at 2.5 mg to 5 mg and wait two hours before taking more.
- Record product name, percentage, and amount used.
State rules differ. Some states set a tolerance range between labeled and tested potency and require a re-test when a product falls outside it. Ask the shop for the certificate of analysis if the label leaves questions open.